Ink set for ink-jet recording

ABSTRACT

An ink jet recording ink set including a plurality of inks, each ink including at least a colorant encapsulating a pigment with a polymer, a penetrating agent and water, wherein the ink set includes a combination of black, yellow, magenta and cyan inks, and wherein the polymer in each of the black, yellow, magenta and cyan inks is a polymer of a polymerizable surface active agent and a monomer, which gives high color density printed image, satisfactory color reproducibility, excellent ejection stability and storage stability.

TECHNICAL FIELD

The present invention relates to an ink set for use in an ink jetrecording method and specifically to an ink set for ink jet recordingwhich can produce high-quality printed images on recording media such asink jet recording exclusive papers, etc., for example, plain papers,coated papers, glazed papers, etc., and which is excellent in thestorage stability. More particularly, the invention relates to (1) anink jet recording ink set, wherein each ink comprises at least acolorant enclosing a pigment and/or a dye with a polymer, and the inkset comprises a combination of black, yellow, magenta and cyan, or acombination further combined with orange and green, and relates to (2)an ink jet recording ink set, wherein each ink comprises at least acolorant enclosing a pigment and/or a dye with a polymer, and the inkset comprises a combination of black ink, yellow ink, magenta ink andcyan ink, each ink comprising at least one kind of ink having adifferent concentration.

BACKGROUND ART

Ink jet recording is a method of recording letters or figures on thesurface of a recording medium by ejecting an ink from a fine nozzle asdroplets. As an ink jet recording system, a method wherein electricsignals are converted to mechanical signals using an electrostrictiveelement and an ink reserved in a nozzle head section is intermittentlyejected to record letters or symbols on the surface of a recordingmedium; and a method wherein a part of an ink reserved in a nozzle headsection and very closing to the ejecting portion is rapidly heated togenerate bubbles, whereby the ink is intermittently ejected by thevolume expansion caused by the bubbles to record letters or symbols onthe surface of a recording medium, etc., have been practically used.

The inks used for such an ink jet recording have been required to havevarious characteristics. For example, the characteristics such as (a)the ink does not cause bleeding upon printing on paper, which is arecording medium, (b) the ink has a good drying property, (c) the inkcan be uniformly printed on the surfaces of various recording media, (d)in multi-color printing, e.g., color printing, etc., adjacent colors arenot mingled, (e) the keeping quality of color images is good, etc., havebeen required.

For the required characteristics such as the above-described (a) to (e),dye inks and pigment inks have been investigated as inks. Since the inksusing dyes are excellent in the color developing property but areinferior in the light resistance and the water resistance, pigment inkshave, recently, been investigated.

In many inks using pigments, it has been investigated to restrainwetting of the surface of paper with ink by mainly restraining thepermeability of ink and to ensure the printing quality by staying theink droplets near the surface of paper, and such a technique has beenput into practical use.

However, with the ink that restrains wetting to paper, there areproblems that the difference in the degree of bleeding depending on thekind of paper is large and, upon printing of a multi-color system suchas a color printing, adjacent colors are intermingled and further thereis a problem that the scrubbing resistance becomes inferior.

For solving these problems, it has been attempted to add a penetratingagent for improving the permeability of ink to paper. For example,examples of using glycol ethers are disclosed. Specifically, JapanesePatent Laid-Open No. 147861/1981 discloses an example of usingtriethylene glycol monomethyl ether, and Japanese Patent Laid-Open No.111165/1997, examples of using an ether such as ethylene glycol,diethylene glycol or triethylene glycol are disclosed. Also, U.S. Pat.No. 5,156,675 proposes the addition of diethylene glycol monobutylether, U.S. Pat. No. 5,183,502 proposes the addition of Surfynol 465(manufactured by Air Products and Chemicals Inc.), which is an acetyleneglycol-based surface active agent, and U.S. Pat. No. 5,196,056 proposesthe use of diethylene glycol monobutyl ether and Surfynol 465 together.Moreover, U.S. Pat. No. 2,083,372 proposes to use ethers of diethyleneglycol for inks.

Also, in the inks using conventional pigments, it has generally beencarried out to disperse the pigment in an aqueous medium using adispersing agent such as a surface active agent, a polymeric dispersingagent, etc. However, there is a problem that it is not easy to improve“the permeability of the ink” while ensuring the dispersion stability ofthe pigment.

Also, in the pigment ink wherein “a pigment dispersion having adispersed pigment” is prepared using a dispersing agent such as asurface active agent, a polymeric dispersing agent, etc., and thepermeability thereof is improved by using the pigment dispersion, sincethe dispersing agent is simply adsorbed to the surface of the pigment,it sometimes happens that when a strong shearing force is applied in thecase of ejecting the ink through a fine nozzle, the dispersing agentadsorbed is released to reduce the dispersibility, whereby “a tendencythat the ejection becomes unstable” occurs. Also, in the case of storingthe pigment ink for a long period of time, the tendency that theejection becomes unstable sometimes happens.

As the means for solving these problems, a method of increasing theaddition amount of the dispersing agent may be considered but in thiscase, since the amount of the dispersing agent, which is dissolved inthe ink without being adsorbed to the surfaces of the pigments, in thecase of printing on a plain paper or a recycled paper using the ink, thephenomena that bleeding is liable to occur, the periphery of a nozzle iswetted with the ink and the ejection is liable to become unstable, etc.,tend to occur.

Furthermore, in the case of printing on a plain paper, a recycled paper,etc., with the above-described pigment ink (the pigment ink wherein “apigment dispersion having a dispersed pigment” is prepared using adispersing agent such as a surface active agent, a polymeric dispersingagent, etc., and the permeability thereof is improved by using thepigment dispersion), there is a tendency that the pigment which is acoloring component is hard to remain on the surfaces of the paper fibersof the surface of the recording medium, whereby there are tendenciesthat a good printed density is not obtained and the color development isnot good. Also, since there is a tendency of increasing the viscosity ofthe ink by the dispersing agent dissolved in the liquid without beingadsorbed on the surface of the pigment from the initial stage and thedispersing agent released from the pigments, the content of the pigmentis frequently limited, thereby particularly with a plain paper and arecycled paper, a sufficient printed density cannot be obtained.Accordingly, good color development cannot be obtained and it isdifficult to obtain printed images of a high quality. Furthermore, whenthe ink is stored for a long period of time in the state of filling in anozzle head, it sometime happens that the dispersion stability isdeteriorated and the ink is hard to be ejected from the nozzle of theprinter.

On the other hand, as the means of attaining the purposes of enhancingthe ejection stability, the dispersion stability, the printing density,the color developing property, etc., an ink using a pigment wherein thesurface is subjected to some treatment has been proposed.

As the ink using the pigment subjected to some treatment, there areproposed, for example, “the ink having pigment particles surfaces ofwhich are subjected to an oxidation treatment” described in JapanesePatent Laid-Open No. 319444/1996, “the ink having the encapsulated finepigment particles” described in Japanese Patent Publication No.94634/1995 and Japanese Patent Laid-Open No. 59715/1996, and “the inkhaving the pigment particles surfaces of which are graft polymerizedwith a polymer” described in Japanese Patent Laid-Open Nos. 339516/1993,302227/1996, 302228/1996 and 81647/1996, but the above-describedpurposes have not yet been sufficiently attained. Also, in JapanesePatent Laid-Open No. 320276/1993, “a method of microencapsulating ahydrophobic powder using an amphiphilic graft polymer” is proposed, butwhen a previously polymerized polymer is used at the microencapsulation,there is a problem that the particle sizes after the encapsulationbecomes too large.

In addition to the above-described propositions, in Japanese PatentLaid-Open Nos. 218015/1996, 295837/1996, 3376/1997, 183920/1996,46075/1998, 292143/1998, 80633/1999, 349870/1999 and 7961/2000, “inkusing a pigment coated with a resin having a film-forming property atroom temperature by a phase inversion emulsification method” isproposed, and in Japanese Patent Laid-Open Nos. 31360/1997, 217019/1997,316353/1997, 104834/1997, 151342/1997, 140065/1998, 152424/1999,166145/1999, 199783/1999 and 209672/1999, “ink using a pigment coatedwith an anionic group-containing polymer compound by an acid depositionmethod” is proposed.

Moreover, in Japanese Patent Laid-Open Nos. 286939/1997, 44852/2000,53897/2000, 53898/2000, 53899/2000 and 53900/2000, “ink using a polymeremulsion wherein polymer fine particles are impregnated with a coloringmaterial by a phase conversion emulsification method” is proposed.

However, in “the colorants obtained by the phase conversionemulsification method or the acid deposition method” described above and“the inks using glycol ethers or the surface active agents such asacetylene glycol-based surface active agents, etc. as penetratingagents” described above, the pigment, which is a coloring component, ishard to remain on the surfaces of the paper fibers of the surface of therecording medium in the case of printing on a plain paper or a recycledpaper. This is, for example, because “the resin, which was not adsorbedon the pigment, exists dissolved in the ink”, or because “the resinadsorbed on the pigment is released to increase the amount of the resindissolved in the ink”. Therefore, a high printing density is hard toobtain and the color development is bad. Also, the phenomena thatbleeding is liable to occur, that the periphery of a nozzle is wettedwith the ink and that the ejection is liable to become unstable, etc.,are liable to occur. Thus, particularly, the image quality in printingon a plain paper or a recycled paper is not yet satisfactory.

Also, it is known that according to the kind of a coloring material andthe permeability of ink, the color reproducing range largely differs,and the dispersion stability of the pigment, particularly, thedispersion stability by allowing to stand for a long period of time isinferior, and also there are large problems that the head is cloggedwith pigments.

As described above, when a pigment is used as a colorant of an ink,since the surface property of the pigment differs in each kind of thepigment, a dispersing method suitable for each pigment must be selectedfor the purpose of obtaining the dispersion stability, by appropriatelychanging the kind and the addition amount of a dispersing agent added.By such a construction of the dispersion, the following problems (1) and(2) occur.

(1) Even when a pigment giving a proper color reproducing range and highchroma is selected as a colorant of ink, the properties of the inkprepared therewith do not fall within the preferred range for ink jet,and after all, there occurs a problem that one cannot take advantage ofthe capability essential to the combination of pigments.

(2) In an ink jet recording ink, the prevention of color bleeding isfrequently attained by imparting a permeability to paper but additivesto ink for imparting a permeability to paper frequently cause theproblems that a dispersing agent adsorbed to a pigment is desorbed tocause aggregates and changes in the properties of the ink, etc.

DISCLOSURE OF THE INVENTION

The present inventors have obtained a knowledge (hereinafter, isreferred to as “the 1st knowledge”) that in an ink jet recording ink setusing pigments for the colorants of inks, good color images can berealized by a combination of the specific pigments. Furthermore, it hasbeen confirmed that enclosing each of the pigments with a polymer toform each colorant can solve the above-described problems.

Also, the inventors have further obtained a knowledge (hereinafter, isreferred to as “the 2nd knowledge”) that in an ink jet recording ink setusing pigments for the colorants of inks, good color images can berealized by a specific combination of the pigments and by using at leastone kind ink having a different addition concentration, for each of“black inks, yellow inks, magenta inks and cyan inks”. Furthermore, ithas been confirmed that by enclosing each of the pigments with a polymerto form each colorant, the above-described problems such as the fixingproperty in the exclusive paper, the difference in the glossy feeling(glossy unevenness), etc., can be solved.

The present inventions are based on the above-described 1st and 2ndknowledges.

A 1st object of the invention is to provide an ink jet recording inkset, wherein the concentrations of the pigments can be optimized, thedesign of the pigment inks can be very easily carried out, a desiredintermediate color can be colored, and good color images can berealized.

A 2nd object of the invention is to provide an ink jet recording ink setexcellent in the dispersion stability of ink.

As the technical construction for attaining the above-described objects,the present invention has a feature that it provides “an ink jetrecording ink set, wherein each ink comprises at least a colorantenclosing a pigment and/or a dye with a polymer, a penetrating agent andwater, and the ink set comprising a combination of black, yellow,magenta and cyan.” Also, the invention has a feature that the ink setcomprises a combination further including orange and green in additionto the above-described 4 colors (black, yellow, magenta and cyan).

Furthermore, as the technical construction of attaining theabove-described objects, the invention has a feature that the abovedescribed “black, yellow, magenta and cyan” comprises:

a combination of at least one kind of a black ink, at least one kind ofa yellow ink, at least one kind of a magenta ink, and at least one kindof a cyan ink; or

a combination of at least one kind of a black ink having a differentaddition concentration, at least one kind of a yellow ink having adifferent addition concentration, at least one kind of a magenta inkhaving a different addition concentration, and at least one kind of acyan ink having a different addition concentration.

Also, the invention has a feature that the pigment used for theabove-described black colorant is C.I. Pigment Black 7, the pigment usedfor the above-described yellow colorant is one kind or two or more kindsof the pigments selected from C.I. Pigment Yellow 55, 74, 110, 128, 150,155 and 180, the pigment used for the above-described magenta colorantis one kind or two or more kinds of the pigments selected from C.I.Pigment Red 122, 202 and 209, and the pigment used for theabove-described cyan colorant is one kind or two or more kinds of thepigments selected from C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4,15:6 and 16.

Also, the invention has a feature that the pigment used for theabove-described orange colorant is one kind or two or more kinds of thepigments selected from C.I. Pigment Oranges 36 and 43 and the pigmentused for the above-described green colorant is one kind or two or morekinds of the pigments selected from C.I. Pigment Greens 7 and 36.

As described above, in the ink jet recording ink set of the invention,by employing a colorant enclosing the specific pigments with a polymerfor each ink and by combining specific 4 colors pigments of black,yellow, magenta and cyan, and further, by adding thereto specificpigments of orange and green, the invention provides an ink jetrecording ink set, wherein the concentrations of the pigments can beoptimized, the design of the pigment inks can be very easily carriedout, a desired intermediate color can be colored, and good color imagescan be realized. Furthermore, in the invention, “the dispersionstability of ink” can be more improved by enclosing each pigment with apolymer.

In an ink jet recording method, color images are expressed by applyingthe two-state control of “print/not print” to color ink composition(s).Accordingly, the number of colors capable of being expressed is limitedby the relation with the resolution, but in the invention, particularly,by adding orange and green, the remarkable working-effect that thenumber of colors capable of being expressed is greatly increased.

Furthermore, in the ink set of the invention, by using pigments for thecolorants, the working effects as described below are obtained. That is,an ink using a pigment for the colorant has a low transparency ascompared with an ink using a dye as the colorant. Accordingly, when inkcompositions of at least two colors are simultaneously printed, thereare the tendencies that the lightness of the printed surface is loweredand the chroma is also lowered. The tendencies become remarkable whenthe attaching amount of the ink per unit area is increased, for example,when red or green is printed.

In the invention, particularly, by using the orange pigment and thegreen pigment, the attached amount of the ink upon printing a red coloror a green color can be lowered, whereby a print having a high lightnessand high chroma can be obtained. This phenomenon is also confirmed inthe case of a dye ink, but the effect is larger in the case of thepigment ink wherein the transparency of the ink composition is low.Also, the effects usually obtained in the case of using pigments ascolorants, that is, the high water resistance and the high weatherresistance can be simultaneously realized.

Also, as described above, in the ink jet recording ink set of theinvention, each ink contain at least the colorant enclosing the pigmentwith a polymer, and the ink set comprises a combination of the specificpigment of 4 colors of at least one kind of a black ink having adifferent addition concentration, at least one kind of a yellow inkhaving a different addition concentration, at least one kind of amagenta ink having a different addition concentration, and at least onekind of a cyan ink having a different addition concentration, therebythe working effects that the concentrations of the pigments can beoptimized, the design of the pigment inks can be very easily carriedout, a desired intermediate color can be colored, and good color imagescan be realized are obtained.

Furthermore, by enclosing each pigment with a polymer, the fixingproperty of ink and the deterioration of images by the difference inglossy feeling are improved, and “the dispersion stability of ink” canbe made further excellent. Also, the effects usually obtained in thecase of using a pigment as a colorant, that is, the high waterresistance and the high weather resistance can be simultaneouslyrealized.

Also, the ink jet recording ink set of the invention has a feature thatthe addition amount of each of the above-described “colorants eachenclosing the pigment and/or the dye with a polymer” is from 0.5 to 30%by weight.

Furthermore, the invention has features that “the polymer enclosing thepigment and/or the dye” described above comprises, as a main component,a polymer selected from the group consisting of a polyacrylic acidester, a styrene-acrylic acid ester copolymer, polystyrene, a polyester,a polyamide, a polyimide, a silicon-containing polymer, and asulfur-containing polymer and that the polymer is a polymer of apolymerizable surface active agent and a monomer.

Also, the invention has features that the above-described polymerizablesurface active agent has a polymerizable group, a hydrophobic group, anda hydrophilic group in its structure; that the polymerizable group isselected from the group consisting of a vinyl group, an acrylic group,an acryloyl group, and a methacryloyl group; and that the hydrophilicgroup is selected from the group consisting of a carbonyl group, acarboxyl group, a hydroxyl group, a sulfonic acid group, and saltsthereof.

Furthermore, the invention has features that “the polymer enclosing thepigment and/or the dye” described above is a polymer having acrosslinked structure, and that the polymer having a crosslinkedstructure described above is a polymer of a dispersing agent having apolymerizable group and a crosslinkable monomer. Also, the invention hasa feature that the colorant enclosing the pigment and/or the dye withthe polymer having the crosslinked structure is obtained by, afterdispersing the pigment and/or the dye in water with the dispersing agenthaving a polymerizable group, adding thereto at least the crosslinkablemonomer and a polymerization initiator to cause polymerization.

Also, the invention has a feature that each ink of the ink jet recordingink set further contains a material, which makes the surface tension 40mN/m or lower, and glycerol. And the invention has a further featurethat the material of making the surface tension 40 mN/m or lower is:

a substance comprising at least one member selected from acetyleneglycol-based surface active agents, acetylene alcohol-based surfaceactive agents, glycol ethers and 1,2-alkylene glycols; or

a substance comprising at least one member selected from acetyleneglycol-based surface active agents and/or acetylene alcohol-basedsurface active agents and at least one member selected from glycolethers and/or 1,2-alkylene glycols.

Also, the invention has features that the above-described “acetyleneglycol-based surface active agents and acetylene alcohol-based surfaceactive agents” are 2,4-dimethyl-5-hexyne-3-ol,2,4,7,9-tetramethyl-5-decyne-4,7-diol and 3,6-dimethyl-4-octyne-3,6-dioland/or said 2,4-dimethyl-5-hexyne-3-ol,2,4,7,9-tetramethyl-5-decyne-4,7-diol and3,6-dimethyl-4-octyne-3,6-diol, having added with at most 30, onaverage, ethyleneoxy groups and/or propyleneoxy groups; that theabove-described glycol ethers are one kind or a mixture of two or morekinds selected from diethylene glycol mono(alkyl having from 4 to 8carbon atoms) ethers, triethylene glycol mono(alkyl having from 4 to 8carbon atoms) ethers, propylene glycol mono(alkyl having from 3 to 6carbon atoms) ethers, and dipropylene glycol mono(alkyl having from 3 to6 carbon atoms) ethers; that the above-described 1,2-alkylene glycolsare 1,2-(alkyl having from 4 to 10 carbon atoms)diols, specifically,1,2-pentanediol and/or 1,2-hexanediol; and that the above-described“propylene glycol mono(alkyl having from 3 to 6 carbon atoms) ethers anddipropylene glycol mono(alkyl having from 3 to 6 carbon atoms) ethersare propylene glycol monobutyl ethers and/or dipropylene glycolmonobutyl ethers.

BEST MODE FOR CARRYING OUT THE INVENTION

As described above, the ink jet recording ink set of the invention has afeature that “in an ink jet recording ink set, wherein each inkcomprises at least a colorant enclosing a pigment and/or a dye with thepolymer, the ink set comprises a combination of black, yellow, magentaand cyan (and further, orange and green)” and also has a feature thatthe above-described “black, yellow, magenta, and cyan” comprise acombination of each at least one kind of black inks, yellow inks,magenta inks, and cyan inks each having a different additionconcentration”.

In the invention, the addition amount of the colorant is preferably from0.5 to 30% by weight, and more preferably from 1.0 to 12% by weight.When the addition amount is less than 0.5% by weight, a proper printingdensity is hard to be ensured and when the addition amount exceeds 30%by weight, the viscosity of the ink is increased and a structuralviscosity occurs in the viscosity characteristics, whereby the ejectionstability tends to become inferior.

(Pigment)

The pigments used for the colorants in the invention are illustrated asfollows.

As inorganic pigments for black, there are carbon blacks (C.I. PigmentBlack 7) such as furnace black, lamp black, acetylene black, channelblack, etc., and iron oxide pigments. Also, as organic pigments forblack, there are black organic pigments such as aniline black (C.I.Pigment black 1), etc. In these pigments, “C.I. Pigment black 7” ispreferred.

The pigments for yellow include C.I. Pigment 1 (Hansa Yellow), 3 (HansaYellow 10G), 12, 13, 14, 17, 24 (Flavanthrone Yellow), 34, 35, 37, 53,55, 65, 73, 74, 81, 83, 93, 94, 95, 97, 98, 99, 108 (AnthrapyrimidineYellow), 109, 110, 113, 117 (copper complex salt pigment), 120, 128, 133(quinophthalone), 138, 139 (isoindolinone), 147, 150, 151, 153 (nickelcomplex salt pigment), 154, 155, 156, 167, 172, 180, etc. In thesepigments, “C.I. Pigment Yellow 55, 74, 93, 109, 110, 128, 150, 155, 156,and 180” are preferred, and more preferred pigments are one or two morekinds of pigments selected from “C.I. Pigment yellow 55, 74, 110, 128,150, 155, and 180”.

The pigments for magenta include C.I. Pigment Red 1 (Para Red), 2, 3(Toluidine Red), 5 (ITR Red), 7, 9, 10, 11, 12, 17, 30, 31, 38(Pyrazolone Red), 42, 88 (thioindigo), 112 (naphthol AS series), 114(naphthol AS-series), 122 (dimethylquinacridone), 123, 144, 149, 150,166, 168 (anthoanthorone orange), 170 (naphthol As-series), 171, 175,176, 177, 178, 179 (perylene maroon), 185, 187, 202, 209(dichloroquinacridone), 219, 224 (perylene series), and 245 (naphthol ASseries); and C.I. Pigment Violet 19 (quinacridone), 23 (DioxazineViolet), 32, 33, 36, 38, 43, 50, etc. In these pigments, “C.I. PigmentViolet 19, C.I. Pigment Red 122, 202, and 209” are preferred, and morepreferred pigments are one or two more kinds of pigments selected from“C.I. Pigment Red 122, 202, and 209”.

The pigments for cyan include C.I. Pigment Blue 15, 15:1, 15:2, 15:3,15:4, 15:6, 16 (nonmetallic phthalocyanine), 18 (alkali blue toner), 25,60 (Threne Blue), 65 (violanthrone), 66 (Indigo), etc. In thesepigments, the use of one kind or two or more kinds of the pigmentsselected from “C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6, and16” is preferred.

The pigments for orange include C.I. Pigment Orange 1, 2, 5, 7, 13, 14,15, 16, 34, 36, 38, 43, etc., and in these pigments, the use of one ortwo or more kinds of the pigments selected from “C.I. Pigment Orange 36and 43” is preferred.

The pigments for green include C.I. Pigment Green 7(PhthalocyanineGreen), 10(Green Gold), 36, 37, etc., and in these pigments, the use ofone or two or more kinds of the pigments selected from “C.I. PigmentGreen 7 and 36” is preferred.

The particle sizes of the above-described pigments are preferably notlarger than 1 μm, and more preferably from 0.01 to 0.15 μm.

(Dye)

As the dyes used for the colorants in the invention, dyes insoluble orsparingly soluble in water are preferred, and practically, there are,for example, oil-soluble dyes, basic dyes, disperse dyes, vat dyes,sulfur dyes, organic solvent-soluble dyes, reactive dyes, etc.

(Polymer Having or Not Having Crosslinked Structure)

The present invention has a feature that the polymer enclosing thepigment and/or the dye comprises, as a main component, a member selectedfrom the group consisting of a polyacrylic acid ester, a styrene-acrylicacid ester copolymer, polystyrene, polyester, a polyamide, a polyimide,a silicon-containing polymer and a sulfur-containing polymer, andfurther has a feature that the polymer is a polymer of a polymerizablesurface active agent and a monomer.

The colorant enclosing a coloring material with the polymer (a polymerhaving a crosslinked structure) for use in the invention can be obtainedby enclosing a coloring material using a polymer having a polymerizablegroup (crosslinking reactive group), a hydrophobic group, and ahydrophilic group in its structure by carrying out a phase conversionemulsification, and further by carrying out a crosslinking reaction witha crosslinking agent.

In more detail, a coloring material, a polymer having a polymerizablegroup (crosslinking reactive group), a hydrophobic group and ahydrophilic group, and a crosslinking agent are added into an organicsolvent, and a neutralizing agent and, if necessary, a surface activeagent (a reactive surface active agent is preferably used as the surfaceactive agent) are added to the solution or the dispersion obtained. Themixture obtained is used as an organic solvent phase, while stirring theorganic solvent phase or water, by adding the water to the organicsolvent phase or by adding the organic solvent phase to the water, aphase conversion emulsification is carried out, thereby the coloringmaterial is enclosed by “the organic phase made of the polymer havingthe crosslinking reactive group and a hydrophilic group and acrosslinking agent”. In this case, a catalyst causing a crosslinkingreaction may be added to any one of the organic solvent phase and water,but when the catalyst is oil-soluble, it is preferred to add thecatalyst to the organic solvent phase and when the catalyst iswater-soluble, it is preferred to add the catalyst to water. Then, aftercarrying out the crosslinking reaction at a definite temperature ofcausing the crosslinking reaction for a definite time, by distilling offthe organic solvent by a general method such as a distillation method, avacuum distillation method, etc., a dispersion wherein the colorantformed by enclosing the coloring material with the polymer having thecrosslinked structure is dispersed in an aqueous phase can be obtained.

The polymer for use in the above-described method in the invention maybe a polymer having at least a polymerizable group (crosslinkingreactive group), a hydrophobic group and a hydrophilic group, andexamples of the polymer include a vinyl-based polymer, a polyacrylicacid ester, a styrene-acrylic acid ester copolymer, polystyrene,polyester, polyamide, polyimide, polyurethane, an amino-based polymer, asilicon-containing polymer, a sulfur-containing polymer, afluorine-containing polymer, an epoxy resin, and a mixture thereof, etc.

The hydrophilic group of the above-described polymer for use in theinvention includes a carbonyl group, a carboxyl group, a hydroxyl group,a sulfone group, a sulfonic acid group, salts thereof, and a quaternaryammonium salt and the hydrophilic group is selected from these groups.

The crosslinking reactive group of the polymer for use in the inventiondescribed above includes a glycidyl group, an isocyanate group, ahydroxyl group, a carboxyl group, and an unsaturated hydrocarbon group,and the group is selected from these groups. The unsaturated hydrocarbongroup described above includes a vinyl group, an allyl group, an acrylicgroup, an acryloyl group, a methacryloyl group, a propenyl group, avinylidene group, and a vinylene group, and the group is selected fromthese groups.

In a preferred embodiment of the invention, as the above-describedpolymer, a vinyl-based polymer, a poly (meth)acrylic acid ester, or astyrene-(meth)acrylic acid copolymer is used. The polymer can beobtained by carrying out a solution polymerization of a (meth)acrylicacid ester monomer having at least one hydrophilic group selected fromthe group consisting of a sulfone group, a sulfonic acid group, acarboxyl group, a hydroxyl group, the salts thereof, and a quaternaryammonium group, a (meth)acrylic acid ester monomer having a crosslinkingreactive group such as a glycidyl group, an isocyanate group, etc., anda monomer copolymerizable with these monomers in a solvent such as analiphatic hydrocarbon-based solvent, an aromatic hydrocarbon-basedsolvent, an ester-based solvent, a ketone-based solvent, analcohol-based solvent, an aprotic solvent, etc., in the existence of apolymerization initiator, for example, a peroxide such as t-butylperoxybenzoate, di-t-butyl peroxide, cumene perhydroxide, acetylperoxide, benzoyl peroxide, lauroyl peroxide, etc.; or an azo compoundsuch as azobisisobutyronitrile, azobis-2,4-dimethyl valeronitrile,azobis-cyclohexane carbonitrile, etc.

In the case of a solution polymerization, a polymerizationchain-transfer agent may be further added. Examples of thepolymerization chain-transfer agent include mercaptans such as octylmercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecylmercaptan, n-tetradecyl mercaptan, t-tetradecyl mercaptan, etc.;xanthogen disulfides such as dimethyl xanthogen disulfide, diethylxanthogen sulfide, diisopropyl xanthogen disulfide, etc.; thiuramdisulfides such as tetramethylthiuram disulfide, tetraethylthiuramdisulfide, tetrabutylthiuram disulfide, etc.; halogenated hydrocarbonssuch as carbon tetrachloride, ethylene bromide, etc.; hydrocarbons suchas pentaphenylethane, etc.; and acrolein, methacrolein, allyl alcohol,2-ethylhexyl thioglycolate, α-terpinene, γ-terpinene, dipentene, and anα-methylstyrene dimer (dimers containing at least 50 parts by weight of2,4-diphenyl-4-mehyl-1-pentene are preferred). Furthermore, there areunsaturated cyclic hydrocarbon compounds such as 9,10-dihydroanthracene,1,4-dihydronaphthalene, indene, 1,4-cyclohexadiene, etc.; unsaturatedheterocyclic compounds such as xanthene, 2,5-dihydrofuran, etc. They maybe used singly or as a combination of two or more kinds of them.

The polymerization is usually carried out at a temperature of from 30 to100° C., and preferably from 50 to 80° C. for from 1 to 10 hours, andthey are appropriately selected according to the kinds of the radicalpolymerization initiator, monomers and the solvent used. Also, it ispreferred that the polymerization is carried out under an inert gasatmosphere such as nitrogen, etc. After the polymerization, thecopolymer formed can be isolated from the reaction liquid by a knownmethod such as a re-precipitation, the solvent removal by distillation,etc. Also, the copolymer obtained can be purified by removing unreactedmonomer, etc., by repeating the re-precipitation, a membrane separationmethod, a chromatographic method, an extraction method, etc. The weightaverage molecular weight of the polymer thus obtained is preferably from1000 to 50,000, and more preferably from 1000 to 30,000 from the viewpoints of easiness of enclosing a coloring material and the easiness ofcarrying out crosslinking.

Examples of the (meth)acrylic acid ester monomer having a hydrophilicgroup include, as an acrylic monomer having a carboxyl group, acrylicacid, methacrylic acid, crotonic acid, ethylacrylic acid, propylacrylicacid, isopropylacrylic acid, itaconic acid, and fumaric acid. In thesemonomers, acrylic acid and methacrylic acid are preferred. As the(meth)acrylic monomer having a sulfonic acid group, there are sulfoethylmethacrylate, butylacrylamide sulfonic acid, etc. Also, as the(meth)acrylic monomer having a phosphone group, there are phosphoethylmethacrylate, etc.

As the (meth)acrylic acid ester having a crosslinking reactive group,there are a polymerizable monomer having a block isocyanate group, amonomer having an epoxy group, a monomer having a1,3-dioxolane-2-one-4-yl group, etc. The polymerizable monomer having ablock isocyanate group can be easily obtained by addition reaction of apolymerizable monomer having an isocyanate group, such as2-methacroyloxyethyl isocyanate, etc., with a known blocking agent.Also, the polymerizable monomer can be produced by addition reaction ofa vinyl-based copolymer having a hydroxyl group and a carboxyl groupwith a compound having an isocyanate group and a block isocyanate group.As the monomer having an epoxy group, there are, for example, glycidyl(meth)acrylate and a (meth)acrylate monomer having an alicyclic epoxygroup. Also, as a monomer having a 1,3-dioxolane-2-one-4-yl group, thereare, for example, 1,3-dioxolane-2-one-4-yl methyl(meth)acrylate and1,3-dioxolane-2-one-4-yl methyl vinyl ether.

The monomer copolymerizable with these monomers include those describedbelow.

For example, there are (meth)acrylic acid esters such as methylacrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, n-butylacrylate, t-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate,lauryl acrylate, benzyl acrylate, methyl methacrylate, ethylmethacrylate, isopropyl methacrylate, n-propyl methacrylate, isobutylmethacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, n-octylmethacrylate, lauryl methacrylate, stearyl methacrylate, tridecylmethacrylate, benzyl methacrylate, etc.; the addition reaction productsof oil fatty acids and (meth)acrylic acid ester monomers having anoxysilane structure, such as the addition reaction product of stearicacid and glycidyl methacrylate, etc.; the addition reaction products ofoxysilane compounds containing an alkyl group having at least 3 carbonatoms and (meth)acrylic acid; styrene-based monomers such as styrene,α-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene,p-tert-butylstyrene, etc.; itaconic acid esters such as benzylitaconate, ethyl itaconate, etc.; maleic acid esters such as dimethylmaleate, diethyl maleate, etc.; fumaric acid esters such as dimethylfumarate, diethyl fumarate, etc.; and acrylonitrile, methacrylonitrile,vinyl acetate, isobornyl acrylate, isobornyl methacrylate, aminoethylacrylate, aminopropyl acrylate, methylaminoethyl acrylate,methylaminopropyl acrylate, ethylaminoethyl acrylate, ethylaminopropylacrylate, aminoethylamide acrylate, aminopropylamide acrylate,aminoethylamide acrylate, aminopropylamide acrylate,methylaminoethylamide acrylate, methylaminopropylamide acrylate,ethylaminoethylamide acrylate, ethylaminopropylamide acrylate, amidemethacrylate, aminoethyl methacrylate, aminopropyl methacrylate,methylaminoethyl methacrylate, methylaminopropyl methacrylate,ethylaminoethyl methacrylate, ethylaminopropyl methacrylate,aminoethylamide methacrylate, aminopropylamide methacrylate,methylaminoethylamide methacrylate, methylaminopropylamide methacrylate,ethylaminoethylamide methacrylate, ethylaminopropylamide methacrylate,hydroxymethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropylacrylate, hydroxymethyl methacrylate, 2-hydroxyethyl methacrylate,2-hydroxypropyl methacrylate, N-methylolacrylamide, allyl alcohol, etc.

The crosslinking agent is a component of causing crosslinking byreacting with the crosslinking reactive group of the above-describedpolymer, and the crosslinking agent having at least two functionalgroups reacting with the crosslinking reactive group of theabove-described polymer in the molecular structure is used.

When the crosslinking reactive group of the above-described polymer is aglycidyl group, it is preferred to use a compound having at least twofunctional groups selected from an amino group, a carboxyl group, ahydroxyl group, an N-methylol group and an N-methylol ether group, andexamples of such a compound include aliphatic amines such as ethyleneamines, N-aminoethylpiperazine, methaxylenediamine,1,3-bis(aminomethyl)cyclohexane, polyamide, etc.; cycloaliphatic aminessuch as para-methanediamine, mesophoronediqamine,bis(4-amino-3-methylcyclohexyl)methane, 2-ethyl-4-methylimidazole, etc.;aromatic amines such as methaphenylenediamine,4,4′-diaminodiphenylamine, 4,4′-diaminodiphenylsulfone, dicyandiamide,etc.; and acid anhydrides such as phthalic anhydride, pyromelliticanhydride, nadic anhydride, etc.

When the crosslinking reactive group of the above-described polymer isan isocyanate group, it is preferred to use a compound having at leasttwo of at least one functional group selected from a carboxyl group, ahydroxyl group, an amino group, and a mercapto group and examples of thecompound include polyols such as polyether polyol, polytetraethyleneglycol, an alkylene oxide copolymer polyol, an epoxy resin-modifiedpolyol, a lactone-based polyester polyol, a condensed polyester polyol,polycarbonate diol, acrylic polyol, polybutadiene polyol, aphosphorus-containing polyol, a halogen-containing polyol, etc.;polyamines such as polyether polyamine, polytetraethylene ether diamine,an alkylene oxide copolymer polyamine, an epoxy-modified polyamine, acondensed polyester polyamine, polycarbonate polyamine, acrylicpolyamine, etc.; and polythiols such as polyether polythiol,polytetramethylene ether dithiol, an alkylene oxide copolymer polythiol,an epoxy resin-modified polyol, a lactone-based polyester polythiol, acondensed polyester polythiol, polycarbonate dithiol, acrylic polythiol,polybutadiene polythiol, a phosphorus-containing polythiol, ahalogen-containing polythiol, etc.

When the crosslinking reactive group of the above-described polymer is ahydroxy group, it is preferred to use a compound having at least two ofat least one functional group selected from a glycidyl group and anisocyanate group.

When the crosslinking reactive group of the above-described polymer isan unsaturated hydrocarbon group, it is preferred to use a compoundhaving at least two of at least one unsaturated hydrocarbon groupsselected from a vinyl group, am allyl group, an acryloyl group, amethacryloyl group, a propenyl group, a vinylidene group, and a vinylenegroup. Examples of such a compound include ethylene glycol diacrylate,diethylene glycol diacrylate, triethylene glycol diacrylate,tetraethylene glycol diacrylate, polyethylene glycol diacrylate, allylacrylate, bis(acryloxyethyl)hydroxyethyl isocyanurate,bis(acryloxy-neopentyl glycol) adipate, 1,3-butylene glycol diacrylate,1,6-hexanediol diacrylate, neopentyl glycol diacrylate, propylene glycoldiacrylate, polypropylene glycol diacrylate,2-hydroxy-1,3-diacryloxypropane, 2,2-bis[4-(acryloxy)phenyl]propane,2,2-bis[4-(acryloxyethoxy)phenyl]propane,2,2-bis[4-(acryloxyethoxy.diethoxy)phenyl]propane,2,2-bis[4-(acryloxy-ethoxy.polyethoxy)phenyl]propane, hydroxypivalicacid neopentyl glycol diacrylate, 1,4-butanediol diacrylate,dicyclopentanyl diacrylate, dipentaerythritol hexa-acrylate,dipentaerythritol monohydroxy penta-acrylate, ditrimethylolpropanetetra-acrylate, pentaerythritol triacrylate, tetrabromobisphenol Adiacrylate, triglycerol diacrylate, trimethylolpropane triacrylate,tris(acryloxyethyl) isocyanurate, ethylene glycol dimethacrylate,diethylene glycol dimethacrylate, triethylene glycol dimethacrylate,tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate,propylene glycol dimethacrylate, polypropylene glycol dimethacrylate,1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate,1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate,2-hydroxy-1,3-dimethacryloxy-propane,2,2-bis[4-(methacryloxy)phenyl]propane,2,2-bis[4-(methacryloxyethoxy)phenyl]propane,2,2-bis[4-(methacryloxy-ethoxydiethoxy)phenyl]propane,2,2-bis[4-(methacryloxyethoxy-polyethoxy)phenyl]propane,tetrabromobisphenol A dimethacrylate, dicyclopentanyl dimethacrylate,dipentaerythritol hexa-methacrylate, glycerol dimethacrylate,hydroxypivalic acid neopentyl glycol dimethacrylate, dipentaerythritolmonohydroxy penta-methacrylate, ditrimethylolpropane tetramethacrylate,pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate,triglycerol dimethacrylate, trimethylolpropane trimethacrylate,tris(methacryloxyethyl) isocyanurate, allyl methacrylate,divinylbenzene, diallyl phthalate, diallyl terephthalate, diallylisophthalate, diethylene glycol bisallyl carbonate, etc.

It is preferred that the above-described crosslinking agent is added tothe organic solvent phase in a range of from 0.01 to 0.1 by weight ratioto the weight of the polymer having a crosslinking reactive group and ahydrophilic group. Weight ratios of less than 0.01 is undesirable sincein this case, the increase of the viscosity, clogging of a nozzle, thereduction of ejection stability, etc., occur in the case of using for along period of time. Also, weight ratios exceeding 0.1 is undesirablesince in the case, lowering of the scrubbing resistance and increase ofthe particle sizes, etc., occur.

As the catalyst used for the crosslinking reaction, a compound havingthe effect of causing or accelerating the reaction may be used. When thecrosslinking reactive group of the above-described polymer is anunsaturated hydrocarbon group and when the compound having at least twounsaturated hydrocarbon groups selected from a vinyl group, an allylgroup, an acryloyl group, a methacryloyl group, a propenyl group, avinylidene group, and a vinylene group is used as the crosslinkingagent, each of an oil-soluble radical polymerization initiator, forexample, a peroxide such as t-butyl peroxybenzoate, di-t-butyl peroxide,cumene perhydroxide, acetyl peroxide, benzoyl peroxide, lauroylperoxide, etc., or an azo compound such as azobis-isobutylnitrile,azobis-2,4-dimethylvaleronitrile, azobis-cyclohexanecarbonitrile, etc.,and a water-soluble radical polymerization initiator such as potassiumpersulfate, ammonium persulfate, sodium persulfate,2,2-azobis(2-methyl-propionamidine)di-hydrochloride, and4,4-azobis(4-cyanovaleric acid) can be used. In addition, the additionamount of the catalyst is appropriately determined.

There is no particular restriction on the organic solvent used for theorganic solvent phase, and an organic solvent dissolving the polymerhaving at least the crosslinking reactive group and the hydrophilicgroup described above may be used. From the viewpoint of the easiness ofdistilling off an organic solvent, an low-boiling organic solvent ispreferably used. For example, there are ketone-based organic solventssuch as acetone, methyl ethyl ketone, etc.; ester-based organic solventssuch as ethyl acetate, etc.; alcohol-based organic solvents such asethanol, isopropyl alcohol, etc.; and aromatic hydrocarbon-based organicsolvents such as benzene, etc.

The addition amount of the polymer having a crosslinking reactive groupand a hydrophilic group is appropriately determined in the range of from0.3 to 1.5 by weight ratio to the coloring material but it is preferredto control and determine the addition amount such that the mean particlesize of the colorant becomes not larger than 400 nm, and preferably notlarger than 200 nm, and the amounts of water-soluble substancesoriginated in the polymer having a crosslinking reactive group and ahydrophilic group in an aqueous phase after production become not largerthan 1000 ppm.

The mixture containing at least the coloring material, the polymerhaving a crosslinking reactive group and a hydrophilic group, and acrosslinking agent in an organic solvent can be prepared by (a) a methodof dispersing the coloring material in an organic solvent phase havingdissolved therein “the polymer having a crosslinking reactive group anda hydrophilic group”, using a dispersing apparatus such as a bead mill,a roll mill, a sand mill, etc., and further dissolving therein thecrosslinking agent and, as the case may be, an oil-soluble catalyst, or(b) a method of dispersing by flashing a dispersion of the coloringmaterial in water (for example, a wet cake of a pigment) in “the polymerhaving a crosslinking reactive group and a hydrophilic group” by thedispersing apparatus as described above, and further dissolving ordispersing the crosslinking agent and, as the case may be, anoil-soluble catalyst.

For the purpose of enhancing the dispersing property of a pigment, adispersing agent or a surface active agent is generally used but in theinvention, a reactive surface active agent is preferably used. Inaddition, the reactive surface agent described above is the same as thepolymerizable surface active agent described hereinbelow. As thereactive surface active agent, a surface active agent which reacts withthe polymer having a crosslinking reactive group and a hydrophilic groupor the crosslinking agent is used. By using the reactive surface activeagent, “the deterioration of the printed images by the generation ofbleeding, etc., on a plain paper and the ejection failure by wetting theperiphery of a nozzle of a printer head”, which are liable to occur withan ink composition using a colorant produced using a generally useddispersing agent or surface active agent, are restrained. In addition,for fining the colorant obtained, it is preferred that the phaseconversion emulsification is carried out while applying ultrasonicwaves.

Other preferred embodiment of the invention is an ink jet recording inkcomposition containing at least a colorant enclosing a coloring materialwith a polymer having a crosslinked structure constituted by a copolymerof a dispersing agent having at least a polymerizable group and acrosslinkable monomer, a water-soluble organic solvent, and water. Theabove-described polymer having a crosslinked structure includes, as amatter of course, a polymer obtained by copolymerizing a dispersingagent having a polymerizable group, a crosslinkable monomer, and amonomer copolymerizable with these monomers.

The colorant obtained by enclosing a coloring material with the polymerhaving the crosslinked structure constituted by at least the copolymerof the dispersing agent having a polymerizable group and thecrosslinkable monomer means an encapsulated particle wherein thecoloring material is in a fine, stable and complete state.

The colorant in the invention formed by enclosing a coloring materialwith the polymer having the crosslinked structure constituted by atleast the copolymer of the dispersing agent having a polymerizable groupand the crosslinkable monomer is excellent in the dispersion stabilityin an aqueous medium made of a water-soluble organic solvent and water.In particular, the colorant has a good dispersion stability in anaqueous medium made of water and a water-soluble organic solventselected from the group consisting of an acetylene glycol and/oracetylene alcohol-based surface active agent, diethylene glycolmonobutyl ether, triethylene glycol monobutyl ether, propylene glycolmonobutyl ether, dipropylene glycol monobutyl ether and/or 1,2-alkyleneglycol. The reason has not yet been clarified but it is presumed thatsince by encapsulating as described above, the enclosing polymer is morestrongly fixed to the coloring material as compared with the case that adispersing agent is simply adsorbed onto the surface of the coloringmaterial by a van der Waals force and the enclosing polymer has acrosslinked structure, whereby the solvent resistance is improved. Inaddition, the above-described theory is used for explaining the contentof the invention to the utmost and the scope of the invention is notlimited by the theory only.

The dispersing agent having a polymerizable group for use in theinvention may be a dispersion containing at least a polymerizable group,a hydrophobic group and a hydrophilic group in its molecular structureand as such a dispersing agent, there are a polymeric dispersing agenthaving introduced therein a polymerizable group and a surface activeagent having introduced therein a polymerizable group.

The polymerizable group may be a functional group, which causes apolymerization reaction such as a radical polymerization, apolyaddition, a polycondensation, etc. The radical polymerizable groupincludes unsaturated hydrocarbon groups such as a vinyl group, an allylgroup, an acryloyl group, a methacryloyl group, a vinylidene group, avinylene group, etc. The polyaddition reactive group includes anisocyanate group and an isothiocyanate group, and as the group reactingwith these groups, there are a hydroxyl group, an amino group, amercapto group, a carboxyl group, etc. The polycondensation reactivegroup is a functional group capable of causing a condensation reactionand includes a carboxyl group, a hydroxyl group, an amino group, analkoxy group, etc.

In a preferred embodiment of the invention, the polymerizable group ispreferably “an unsaturated hydrocarbon group which is a radicalpolymerizable group” and it is preferred that such an unsaturatedhydrocarbon group is selected from the group consisting of a vinylgroup, an allyl group, an acrylic group, an acryloyl group, amethacryloyl group, a propenyl group, a vinylidene group, and a vinylenegroup.

Also, in a preferred embodiment of the invention, it is preferred thatthe hydrophilic group is selected from the group consisting of acarboxyl group, a carbonyl group, a hydroxyl group, a sulfone group, asulfonic acid group, salts thereof, and a quaternary ammonium salt.

As the polymeric dispersing agent having introduced therein apolymerizable group, the following dispersing agents each obtained byintroducing a polymerizable group into a synthetic polymer can be used.Specific examples of the synthetic polymer include acrylic resins suchas polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, anacrylic acid-acrylonitrile copolymer, a potassium acrylate-acrylonitrilecopolymer, a vinyl acetate-acrylic acid ester copolymer, an acrylicacid-acrylic acid ester copolymer, etc.; styrene-acrylic resins such asa styrene-acrylic acid copolymer, a styrene-methacrylic acid copolymer,a styrene-methacrylic acid-acrylic acid copolymer, astyrene-α-methylstyrene-acrylic acid copolymer, astyrene-α-methylstyrene-acrylic acid ester copolymer, etc.; astyrene-maleic acid copolymer; a styrene maleic anhydride copolymer; avinylnaphthalene-acrylic acid copolymer; a vinylnaphthalene-maleic acidcopolymer; and vinyl acetate-based copolymers such as a vinylacetate-ethylene copolymer, a vinyl acetate-fatty acid vinylethylenecopolymer, a vinyl acetate-malic acid ester copolymer, a vinylacetate-crotonic acid copolymer, a vinyl acetate-acrylic acid copolymer,etc.; and salts thereof. In these polymers, particularly, the copolymerof a monomer having a hydrophobic group and a monomer having ahydrophilic group and the polymer made of a monomer having a hydrophobicgroup and a hydrophilic group together in the molecular structure arepreferred.

In the invention, as a preferred embodiment, a polymerizable surfaceactive agent is used as the dispersion having a polymerizable group.

The polymerizable surface active agent for use in the invention has atleast a polymerizable group, a hydrophobic group, and a hydrophilicgroup in the molecular structure.

In the polymerizable surface active agent for use in the invention, itis preferred that the hydrophilic group thereof is selected from thegroup consisting of a sulfone group, a sulfonic acid group, a carboxylgroup, a carbonyl group, a hydroxyl group, salts thereof, and aquaternary ammonium salt. Also, it is preferred that the polymerizablegroup is an unsaturated hydrocarbon group and more specifically isselected from the group consisting of a vinyl group, a vinyl group, anallyl group, an acrylic group, an acryloyl group, a methacryloyl group,a propenyl group, a vinylidene group, and a vinylene group. Specificexamples of the polymerizable surface active agent include “the anionicallyl derivatives” as described in Japanese Patent Publication Nos.46291/1974 and 24142/1989, and Japanese Patent Laid-Open No.104802/1987, “the anionic propenyl derivatives” as described in JapanesePatent Laid-Open No. 221431/1987, “the anionic acrylic acid derivatives”as described in Japanese Patent Laid-Open Nos. 34947/1987 and11525/1980, “the anionic itaconic acid derivatives” as described inJapanese Patent Publication No. 34898/1971 and Japanese Patent Laid-OpenNo. 30284/1976, “the anionic maleic acid derivatives” as described inJapanese Patent Publication No. 4157/1976 and Japanese Patent Laid-OpenNo. 30284/1976, “the nonionic allyl derivatives” as described inJapanese Patent Laid-Open No. 104802/1987, “nonionic propenylderivatives” as described in Japanese Patent Laid-Open No. 100502/1987,“the nonionic acrylic acid derivatives” as described in Japanese PatentLaid-Open No. 28208/1981, “the nonionic itaconic acid derivatives” asdescribed in Japanese Patent Publication No. 12681/1984, “the nonionicderivatives” as described in Japanese Patent Publication No. 65824/1992,and “the cationic allyl derivatives” as described in Japanese PatentPublication No. 65824/1992.

Since the polymerizable surface active agent adsorbs on the surfaces ofcoloring material particles and is excellent in the dispersibility (thatis, the occurrence of the aggregation of the particles each other can beprevented) under the polymerization condition thereafter, thepolymerizable surface active agent is useful in the point that theencapsulated particles are easily formed.

In the invention, as the polymerizable surface active agent, thecompounds represented by following formula (I) or (II) are preferred. Inaddition, the polymerizable surface active agents shown by the formula(I) are disclosed in Japanese Patent Publication Nos. 320276/1993 and316909/1998.

In the above formula (I), R represents a hydrogen atom or a hydrocarbongroup having from 1 to 12 carbon atoms; n represents a number of from 2to 20; and M represents an alkali metal, an ammonium salt or analkanolamine.

In the above formula (II), R¹ represents a hydrogen atom or ahydrocarbon group having from 1 to 12 carbon atoms; X represents —SO₃NH₄or —H; and n represents a number of from 2 to 20.

In addition, R¹ is preferably C₉H₁₉— or C₈H₁₇—.

By appropriately controlling R and n in the formula (I), it is possibleto correspond to the extent of the hydrophilic property or thehydrophobic property of the surface of the coloring material. Thepreferred polymerizable surface active agent shown by the formula (I) ispractically the compounds represented by following formulae (III) to(VI). They can be used singly or as a mixture of two or more kinds ofthem.

As the polymerizable surface active agent shown by the formula (I),commercially available products can be used. For example, “SE-10N” ofAdekarea Soap SE Series of ASAHI DENKA KOGYO K. K. corresponds to thecompound shown by the following formula (III), wherein R is C₉H₁₉, n is10, and M is NH₄. Also, “SE-20N” is the same as “SE-10N” but n is 20.

In a preferred embodiment of the invention, fine and stable encapsulatedparticles each formed by enclosing each coloring material with thepolymer of the polymerizable surface active agent shown by the formula(I) or (II), the crosslinkable monomer, and the monomer copolymerizablewith these monomers are used.

The fine and stable encapsulated particles of the coloring material arestably dispersed in an aqueous medium. Since the polymerizable surfaceactive agent shown by the formula (I) or (II) is excellent in theadsorbing property to the surfaces of the coloring material particlesand the dispersibility (that is, the occurrence of the aggregation ofthe particles each other can be prevented) under the polymerizationcondition thereafter, the polymerizable surface active agent is usefulin the point that the encapsulated particles are easily formed.

As the polymerizable surface active agent, other commercially availableproducts than the above-described commercially available products can beused. For example, there are Aquaron HS Series (Aquaron HS-05, HS-10,HS-20, and HS-1025), Aquaron RN Series (RN-10, RN-20, RN-30. RN-50, andRN-2025), and New Frontier Series (New Frontier N-177E and S-510) ofDAI-ICHI KOGYO SEIYAKU CO., LTD., and Adekarea Soap NE Series (NE-10,NE-20, NE-30. NE-40, and NR-50) of ASAHI DENKA KOGYO K. K.

The addition amount of the polymerizable surface active agent is in therange of preferably from about 10 to 150% by weight, and more preferablyfrom about 20 to 100% by weight to the coloring material. By theaddition amount of the polymerizable surface active agent to at least10% by weight, the dispersion stability of the ink composition can beimproved. Also, when the upper limit of the addition amount thereof isnot more than 150% by weight, the generation of the polymerizablesurface active agent non-adsorbed to the coloring material isrestrained, and the generation of a polymer other than the encapsulatedparticles can be prevented, whereby the ejection stability of the inkcomposition can be improved.

As the crosslinkable monomer for use in the invention, any monomershaving a high copolymerizable property with the polymerizable surfaceactive agent can be used.

As the crosslinkable monomer for use in the invention, a compound havingat least two of at least one unsaturated hydrocarbon group selected froma vinyl group, an allyl group, an acrylic group, an acryloyl group, amethacryloyl group, a propenyl group, a vinylidene group, and a vinylenegroup is preferably used, and examples of such a compound includeethylene glycol diacrylate, diethylene glycol diacrylate, triethyleneglycol diacrylate, tetraethylene glycol diacrylate, polyethylene glycoldiacrylate, allyl acrylate, bis(acryloxyethyl)hydroxyethyl isocyanurate,bis(acryloxyneopentyl glycol) adipate, 1,3-butylene glycol diacrylate,1,6-hexanediol diacrylate, neopentyl glycol diacrylate, propylene glycoldiacrylate, polypropylene glycol diacrylate,2-hydroxy-1,3-diacryloxypropane, 2,2-bis[4-(acryloxy)phenyl]propane,2,2-bis[4-(acryloxyethoxy)phenyl]-propane,2,2-bis[4-(acryloxyethoxy.diethoxy)phenyl]propane,2,2-bis[4-(acryloxyethoxy.polyethoxy)phenyl]propane, hydroxypivalic acidneopentyl glycol diacrylate, 1,4-butanediol diacrylate, dicyclopentanyldiacrylate, dipentaerythritol hexa-acrylate, dipentaerythritolmonohydroxy penta-acrylate, ditrimethylolpropane tetra-acrylate,pentaerythritol triacrylate, tetrabromobisphenol A diacrylate,triglycerol diacrylate, trimethylolpropane triacrylate,tris(acryloxyethyl) isocyanurate, ethylene glycol dimethacrylate,diethylene glycol dimethacrylate, triethylene glycol dimethacrylate,tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate,propylene glycol dimethacrylate, polypropylene glycol dimethacrylate,1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate,1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate,2-hydroxy-1,3-dimethacryloxy-propane,2,2-bis[4-(methacryloxy)phenyl]propane,2,2-bis[4-(methacryloxyethoxy)phenyl]propane,2,2-bis[4-(methacryloxy-ethoxypolyethoxy)phenyl]propane,tetrabromobisphenol A dimethacrylate, dicyclopentanyl dimethacrylate,dipentaerythritol hexamethacrylate, glycerol dimethacrylate,hydroxypivalic acid neopentyl glycol dimethacrylate, dipentaerythritolmonohydroxy penta-methacrylate, ditrimethylolpropane tetra-methacrylate,pentaerythritol trimethacrylate, pentaerythritol tetra-methacrylate,triglycerol dimethacrylate, trimethylolpropane trimethacrylate,tris(methacryloxyethyl) isocyanate, allyl methacrylate, divinylbenzene,diallyl phthalate, diallyl terephthalate, diallyl isophthalate,diethylene glycol bisallyl carbonate, etc.

The addition amount of the above-described crosslinkable monomer is inthe range of preferably from 0.1 to 50% by weight, and more preferablyfrom 0.1 to 10% by weight as the constitution ratio of the enclosingpolymer. When the addition amount is less than 0.1% by weight, theincrease of the viscosity, clogging of a nozzle, and the deteriorationof the ejection stability undesirably occur in the case of using for along period of time. Also, when the addition amount exceeds 50% byweight, the desired colorant is undesirably hard to obtain.

In the invention, as the monomer copolymerizable with the polymerizablesurface active agent and the crosslinkable monomer, a radicalpolymerizable monomer, which is generally used, can be used. As theradical polymerizable monomer, there is a monomer having at least oneunsaturated hydrocarbon group such as a vinyl group, an allyl group, anacrylic group, a methacrylic group, a vinylidene group, a vinylenegroup, etc., which are radical polymerizable groups, in the molecule.

Specific examples of the radical polymerizable monomer include styreneand styrene derivatives such as methylstyrene, dimethylstyrene,chlorostyrene, dichlorostyrene, bromostyrene, p-chloromethylstyrene,divinylbenzene, etc.; acrylic acid and monofunctional acrylic acidesters such as methyl acrylate, ethyl acrylate, n-butyl acrylate,butoxyethyl acrylate, benzyl acrylate, phenyl acrylate, phenoxyethylacrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicylopentinylacrylate, dicyclopentinyloxyethyl acrylate, tetrahydrofurfuryl acrylate,isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,2-acryloyloxyethyl succinate, 2-acryloyloxyethyl phthalate, caprolactoneacrylate, glycidyl acrylate, etc.; methacrylic acid and monofunctionalmethacrylic acid esters such as methyl methacrylate, ethyl methacrylate,n-butyl methacrylate, 2-ethylhexyl methacrylate, butoxymethylmethacrylate, benzyl methacrylate, phenyl methacrylate, phenoxyethylmethacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate,dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate,tetrahydrofurfuryl methacrylate, isobornyl methacrylate, 2-hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate,glycerol methacrylate, 2-methacryloyloxyethyl succinate,2-methacryloyloxyethyl phthalate, caprolactone methacrylate, glycidylmethacrylate, etc.; allyl compounds such as allylbenzene,allyl-3-cyclohexane propionate, 1-allyl-3,4-dimethoxybenzene,allylphenoxy acetate, allylphenyl acetate, allyl cyclohexane, allylpolyhydric carboxylate, etc.: and monomers having a radicalpolymerizable group such as acrylonitrile, methacrylonitrile, maleicanhydride, N-substituted maleimides, cyclic olefins, etc.

Also, there are triglycerol diacrylate, trimethylolpropane triacrylate,tris(acryloxyethyl) isocyanurate, ethylene glycol dimethacrylate,diethylene glycol dimethacrylate, triethylene glycol dimethacrylate,tetraethylene glycol dimethacrylate, polyethylene glycol dimethacrylate,propylene glycol dimethacrylate, polypropylene glycol dimethacrylate,1,3-butylene glycol dimethacrylate, 1,4-butanediol dimethacrylate,1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate,2-hydroxy-1,3-dimethacryloxy-propane,2.2-bis[4-(methacryloxy)phenyl]propane,2,2-bis[4-(methacryloxyethoxy)phenyl]propane,2,2-bis[4-(methacryloxy-diethoxy)phenyl]propane,2,2-bis[4-(methacryloxypolyethoxy)-phenyl]propane, tetrabromobisphenol Adimethacrylate, dicyclopentanyl dimethacrylate, dipentaerythritolhexamethacrylate, glycerol dimethacrylate, hydroxypivalic acid neopentylglycol dimethacrylate, dipentaerythritol monohydroxy dimethacrylate,ditrimethylolpropane tetramethacrylate, pentaerythritol trimethacrylate,pentaerythritol tetra-methacrylate, triglycerol dimethacrylate,trimethylolpropane trimethacrylate, tris(methacryloxyethyl)isocyanurate, allyl methacrylate, divinylbenzene, diallyl phthalate,diallyl terephthalate, diallyl isophthalate, diethylene glycolcarbonate, etc.

Since the polymerizable surface active agent shown by the formula (I) isa monomer having a high electron donating property, as the monomer used,a monomer having a high electron accepting property is preferred. Asspecific examples of the monomer having a high electron acceptingproperty, there are acrylonitrile, fumaronitrile, fumaric acid diesterssuch as fumaric acid dibutyl ester, etc.; maleic acid diesters such asmaleic acid dibutyl ester, etc.; and vinylidene cyanide. They can beused singly or as a mixture of two or more kinds thereof.

The addition amount of the monomer is in the range of preferably fromabout 2 to 15 by molar ratio and more preferably from 3 to 12 by molarratio to the polymerizable surface active agent. By making the additionamount of the monomer at least 2 by molar ratio, the encapsulatedcoloring material particles become excellent in the dispersion stabilityin an aqueous medium. Also, by making the addition amount of the monomernot more than 15 by molar ratio, the monomer can be sufficientlydissolved in the polymerizable surface active agent-adsorbed layer andthus since the generation of a monomer insoluble in water and theoccurrence of the relative reduction of the amount of an ionic repulsinggroup can be restrained, the dispersion stability of the ink compositioncan be increased.

As the polymerization initiator for use in the invention, awater-soluble polymerization initiator such as potassium persulfate,sodium persulfate, ammonium persulfate,2,2-azobis(2-methylpropionamidine) dihydrochloride, and4,4-azobis(4-cyanovaleric acid), etc., is used.

As mentioned above, the preferred embodiments of the invention wereexplained by mainly referring to “the polymer having the crosslinkedstructure” as the polymer used in the invention, but in the invention isnot limited to the embodiments only and “a polymer without having acrosslinked structure” described below can be used.

That is, in the invention, as the polymer enclosing a pigment and/or adye, there is a copolymer of a dispersing agent having a polymerizablegroup and a copolymerizable monomer, which is described later in detail.

A colorant enclosing a pigment and/or a dye with the above-describedcopolymer of the dispersion having a polymerizable group and thecopolymerizable monomer is suitably obtained by, after dispersing thepigment and/or the dye in water with the dispersing agent having apolymerizable group, adding the polymerizable monomer and apolymerization initiator to cause polymerization.

Since as an ink jet recording ink, it is preferred that the particlesizes are uniform from the viewpoints of preventing clogging a nozzleand ensuring the stability of ejection of the ink, it is preferred thatthe colorant enclosing a pigment and/or a dye with the polymer isproduced by an emulsion polymerization method.

In the case of using pigment, it is preferred that the colorantenclosing the pigment with the polymer is obtained by dispersing thepigment in water with the dispersing agent having a polymerizable groupand thereafter, carrying out the emulsion polymerization in water usinga monomer (the copolymerizable monomer) copolymerizable with thedispersing agent. Also, the colorant enclosing a dye with the polymer ispreferably obtained by a method of directly dissolving a dye insolubleor sparingly soluble in water, such as an oil-soluble dye, a dispersedye, a vat dye, a reactive dye, etc., in the monomer, and obtaining byan emulsion polymerization. The emulsion polymerization can be carriedout using an ordinary method, and the polymerization is proceeded by afree radical generated by the thermal decomposition of a water-solublepolymerization initiator in the existence of an emulsifying agent.

It is preferred that the above-described copolymerizable monomer is acompound having an unsaturated group in the structure and it isparticularly preferred that the unsaturated group is selected from thegroup consisting of a vinyl group, an allyl group, an acryloyl group, amethacryloyl group, a propenyl group, an acrylamide group, a vinylamidegroup, a vinylidene group, and a vinyl group. More practically, anymonomer having a high copolymerizing property with the dispersing agenthaving a polymerizable group can be used, and a radical polymerizablemonomer, which is generally used, can be used.

As the radical polymerizable monomer, there are monomers each having inthe molecule at least one unsaturated hydrocarbon group such as a vinylgroup, an allyl group, an acryloyl group, a methacryloyl group, apropenyl group, an acrylamide group, a vinylamide group, a vinylidenegroup, a vinylene group, etc.

Specific examples of the radical polymerizable monomer include styreneand styrene derivatives such as methylstyrene, dimethylstyrene,chlorostyrene, dichlorostyrene, bromostyrene, p-chloromethylstyrene,divinylbenzene, etc.; acrylic acid and monofunctional acrylic acidesters such as methyl acrylate, ethyl acrylate, n-butyl acrylate,butoxyethyl acrylate, benzyl acrylate, phenyl acrylate, phenoxyethylacrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, dicylopentenylacrylate, dicyclopentenyloxyethyl acrylate, tetrahydrofurfuryl acrylate,isobornyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate,2-acryloyloxyethyl succinate, 2-acryloyloxyethyl phthalate, caprolactoneacrylate, glycidyl acrylate, etc.; methacrylic acid and monofunctionalmethacrylic acid esters such as methyl methacrylate, ethyl methacrylate,n-butyl methacrylate, 2-ethylhexyl methacrylate, butoxymethylmethacrylate, benzyl methacrylate, phenyl methacrylate, phenoxyethylmethacrylate, cyclohexyl methacrylate, dicyclopentanyl methacrylate,dicyclopentenyl methacrylate, dicyclopentenyloxyethyl methacrylate,tetrahydrofurfuryl methacrylate, isobornyl methacrylate, 2-hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate,glycerol methacrylate, 2-methacryloyloxyethyl succinate,2-methacryloyloxyethyl phthalate, caprolactone methacrylate, glycidylmethacrylate, etc.; aminoethyl acrylate, aminopropyl acrylate,methylaminoethyl acrylate, methylaminopropyl acrylate, ethylaminoethylacrylate, ethylaminopropyl acrylate, aminoethylamide acrylate,aminopropylamide acrylate, methylaminoethylamide acrylate,methylaminopropylamide acrylate, ethylaminoethylamide acrylate,ethylaminopropylamide acrylate, amide methacrylate, aminoethylmethacrylate, aminopropyl methacrylate, methylaminoethyl methacrylate,ethylaminopropyl methacrylate, aminoethylamide methacrylate,aminopropylamide methacrylate, methylaminoethylamide methacrylate,methylaminopropylamide methacrylate, ethylaminoethylamide methacrylate,ethylaminopropylamide methacrylate, hydroxymethyl acrylate,hydroxymethyl methacrylate, N-methylol acrylamide; allyl compounds suchas allyl alcohol, allyl benzene, allyl-3-cyclohexane propionate,1-allyl-3,4-dimethoxybenzene, allylphenoxy acetate, allylphenyl acetate,allyl cyclohexane, allyl polyhydric carboxylates, etc.; fumaric acid,maleic acid, itaconic acid, and the esters of them; and monomers havinga radical polymerizable group, such as acrylonitrile, methacrylonitrile,maleic anhydride, N-substituted maleimides, cyclic olefins, etc.

Particularly, as the copolymerizable monomer, a monomer having ahydrophilic group (e.g., a carboxyl group, a sulfonic acid group, ahydroxyl group, an amide group, and a phosphone group) is preferablyused.

Examples of the monomer having a carboxyl group include acrylic acid,methacrylic acid, crotonic acid, ethacrylic acid, propylacrylic acid,isopropylacrylic acid, 2-acryloxyethyl succinic acid. 2-acryloxyethylphthalic acid, 2-methacryloxyethyl succinic acid, 2-methacryloxyethylphthalic acid, itaconic acid, fumaric acid, and maleic acid. In thesemonomers, acrylic acid and methacrylic acid are preferred.

Examples of the monomer having a sulfonic acid group include4-styrenesulfonic acid and the salts thereof, vinylsulfonic acid and thesalts thereof, sulfoethyl acrylate and the salts thereof, sulfoethylmethacrylate and the salts thereof, sulfoalkyl acrylates and the saltsthereof, sulfoalkyl methacrylates and the salts thereof, sulfopropylacrylate and the salts thereof, sulfopropyl methacrylate and the saltsthereof, sulfoaryl acrylate and the salts thereof, sulfoarylmethacrylate and the salts thereof, butylamidosulfonic acid and thesalts thereof, and 2-acrylamido-2-methylpropane sulfonic acid and thesalts thereof.

Examples of the monomer having a hydroxyl group include 2-hydroxyethylacrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate,2-hydroxypropyl methacrylate, 2-hydroxybutyl acrylate, 2-hydroxybutylmethacrylate, polyethylene glycol 400 acrylate, polyethylene glycol 400methacrylate, N-hydroxyethyl acrylate, and N-hydroxyethyl methacrylate.

Examples of the monomer having an amide group include acrylamide,methacrylamide, aminopropylamide acrylate, aminopropylamidemethacrylate, aminoethylamide acrylate, aminoethylamide methacrylate,and vinylpyrrolidone. As the monomer having a phosphone group, there arephosphoethyl methacrylate, etc.

Since the polymerizable surface active agent shown by the formula (I),which is preferred as the dispersing agent having a polymerizable group(see the above description), is a monomer having a high electrondonating property, the monomer having a high electron accepting propertyis preferred as the copolymerizable monomer used.

As the specific examples of the monomer having a high electron acceptingproperty, there are acrylonitrile, fumaronitrile, fumaric acid diesterssuch as fumaric acid dibutyl ester, etc.; maleic acid diesters such asmaleic acid dibutyl ester, etc.; maleimides such as N-phenylmaleimide,etc., and vinylidene cyanide, etc. They may be used singly or as amixture of two or more kinds of them.

The addition amount of the copolymerizable monomer is in the range ofpreferably from about 2 to 15 by molar ratio, and more preferably fromabout 3 to 12 by molar ratio to the dispersing agent having apolymerizable group. By making the addition amount at least 2 by molarratio, the encapsulated pigment particles formed have excellentdispersion stability in an aqueous medium. Also, by making the additionamount not more than 15 by molar ratio, the monomer can be sufficientlydissolved in the adsorbed layer of the dispersing agent having apolymerizable group, and since the generation of a polymer insoluble inwater and the occurrence of the relative reduction of the amount of anionic repulsing group can be restrained, the working effect that thedispersion stability of the ink is increased is obtained.

As the polymerization initiator for obtaining the copolymer of thedispersing agent having a polymerizable group and the copolymerizablemonomer, there are suitably potassium persulfate, ammonium persulfate,sodium persulfate, 2,2-azobis(2-methylpropionamidine)di-hydrochloride,and 4,4-azobis(4-cyanovaleric acid), etc.

Also, in the emulsion polymerization, a chain transfer agent can beused. As the chain transfer agent, there are, in addition to t-dodecylmercaptan, n-dodecyl mercaptan, n-octyl mercaptan, xanthogens such asdimethylxanthogen disulfide, dibutylxanthogen disulfide, etc.;dipentene, indene, 1,4-cyclohexadiene, dihydrofuran, xanthene, etc.

As a dispersing method of the pigment and/or the dye in water, adispersing method by a method of ultrasonic wave dispersion, a beadmill, a sand mill, a roll mill, etc., can be used.

Particularly, in the case of using the pigment, it is preferred to use adispersing apparatus such as a bead mill, s sand mill, a roll mill,etc., since fine particles of the colorant can be obtained.

(Example of Preparing Colorant Enclosing a Coloring Agent With Polymer)

In the invention, the colorant enclosing a pigment with the polymerhaving a crosslinked structure constituted of the polymerizable surfaceactive agent, the crosslinkable monomer, and the monomer copolymerizablewith these monomers can be produced as follows.

Fixing the polymerizable surface active agent to the pigment, that is,the encapsulation of the pigment is carried out by adding the pigmentand the polymerizable surface active agent to “an aqueous organicsolvent or water”, after wet grinding by ultrasonic waves, a ball mill,or a sand grinder, while, if necessary, continuing the grindingtreatment, adding the crosslinkable monomer and other copolymerizablemonomer and/or the polymerization initiator, and carrying out thepolymerization reaction at a temperature of from 40 to 100° C. for from10 to 60 hours.

By the above operations, encapsulated pigment particles formed byenclosing the pigment with the polymer having a crosslinked structurecan be obtained. The addition amount of the polymerization initiator ispreferably from 0.1 to 10% by weight, and more preferably from 1 to 5%by weight to the monomers. As a preferred production method, a methodaccording to the production method described in Japanese PatentLaid-Open No. 316909/1998 can be used.

The method of fixing the polymeric dispersing agent having apolymerizable group to the pigment, that is the production method of theencapsulation of the pigment can be carried out according to theabove-described production method.

The addition amount of the colorant in the invention is preferably from0.5 to 30% by weight, and more preferably from 1.0 to 12% by weight asdescribed above. When the addition amount is less than 0.5% by weight,the printing density is hard to be ensured, and, on the other hand, whenthe addition amount exceeds 30% by weight, there are undesirabletendencies that the viscosity of the ink is increased and the ejectionstability becomes bad. In addition, the particle sizes of the colorantare preferably not larger than 400 nm and more preferably not largerthan 200 nm.

(Inks of the Ink Jet Recording Ink Set)

The ink of the ink jet recording ink set of the invention contains asubstance making the surface tension of the ink 40 mN/m or lower andglycerol, wherein the substance making the surface tension 40 mN/m orlower comprise at least one member selected from acetylene glycol-basedsurface active agents and/or acetylene alcohol-based surface activeagents, and glycol ethers and/or 1,2-alkylene glycols.

The ink composition containing: at least the colorant enclosing acoloring material with the polymer having a crosslinked structure; atleast one kind of compound selected from the group consisting of theacetylene glycol-based surface active agents and/or the acetylenealcohol surface active agents, glycol ethers (diethylene glycolmonobutyl ether, triethylene glycol monobutyl ether, propylene glycolmonobutyl ether, dipropylene glycol monobutyl ether, etc.) and/or1,2-alkylene glycols; and water is excellent in the dispersion stabilityand the ejection stability, does not cause clogging of nozzle for a longperiod of time, and can give stabilized prints.

In the case of using the acetylene alcohol-based surface active agent, adissolution aid can be used in combination. As the dissolution aid,there are preferably 1,3-dimethyl-2-imidazolidinone,N-methyl-2-pyrrolidone, and 2-pyrrolidone.

Furthermore, high-quality images excellent in the color developingproperty, which has a good drying property after printing, does notcause bleeding, and has a high printing density on a recording mediumsuch as a plain paper, a recycled paper, a coated paper, a glazed paper,etc., can be obtained. Also, the fixing property and the difference ofthe glossy feeling by color and density on an exclusive paper areconsiderably improved.

In general, in the case of dispersing a pigment, a dispersing agent suchas a surface active agent and a polymeric dispersing agent is used, butsince such a dispersing agent is only adsorbed on a coloring material,usually, by a environmental factor, the dispersing agent is liable to bereleased from the surface of the coloring material.

On the other hand, in the invention, as described above, it isconsidered that by enclosing the coloring material with the polymerhaving a crosslinked structure, the polymer enclosing the coloringmaterial is strongly fixed to the coloring material, the polymer is hardto be released from the coloring material.

The above-described point is explained in detail. In an ink wherein apigment dispersion dispersing a pigment using a dispersing agent such asa surface active agent, a polymeric dispersing agent, etc., is used andthe permeability is improved by a penetrating agent such as an acetyleneglycol-based surface active agent, an acetylene alcohol surface activeagent, glycol ethers (such as diethylene glycol monobutyl ether,triethylene glycol monobutyl ether, propylene glycol monobutyl ether,dipropylene glycol monobutyl ether, etc.), a 1,2-alkylene glycol, etc.,by a strong shearing force applied in the case of ejected through a finenozzle, there is a tendency that the dispersing agent is easily releasedfrom the surface of the pigment to deteriorate and the ejection becomesunstable.

On the other hand, in the ink using the colorant in the invention, sucha phenomenon does not occur and ink is stably ejected for a long periodof time. Also, since by enclosing the coloring material with the polymerhaving a crosslinked structure, the polymer enclosing the coloringmaterial is more strongly fixed to the coloring material and is hard tobe released from the coloring material, and the polymer has thecrosslinked structure, a good solvent resistance is obtained, wherebythe acceleration of the release of the polymer from the coloringmaterial and swelling of the polymer by the above-described penetratingagent are hard to occur. Accordingly, the working effect of excellent inthe dispersion stability is obtained for a long period of time.

Also, in an ink wherein a pigment dispersion having a dispersed pigmentusing a dispersing agent such as a surface active agent or a polymericdispersing agent, etc., is used and the permeability is improved, ingeneral, there is a tendency of increasing the viscosity of the ink bythe dispersion, which is dissolved in the liquid without being adsorbedon the surface of the pigment from the beginning of dispersing and thedispersing agent released from the pigment thereafter, thereby thecontent of the pigment is frequently restricted. Therefore, in a plainpaper and a recycled paper, it frequently happens that a sufficientprinting density cannot be obtained and good color development is notobtained.

On the other hand, as described above, in the colorant in the invention,since by enclosing a coloring material with the polymer having acrosslinked structure, the polymer enclosing the coloring material ismore strongly fixed to the coloring material, the polymer is hard to bereleased from the coloring material, and thus the viscosity of the inkis not increased and lowering of the viscosity of the ink is easy,whereby the ink has the advantage that more colorant can contain, andthus a sufficient printing density can be obtained on a plain paper anda recycled paper. Also, since the polymer enclosing the pigment is morestrongly fixed to the coloring material, fixing in an exclusive paper isvery good, about the difference of the glossy feeling originated in thecoloring material, ununiform feeling does not occur and a goodimpression can be given.

The above-described reason is used for explaining the content of theinvention to the utmost and the scope of the invention is not limited bythe reason only.

When the above-described 1,2-alkylene glycol is 1,2-pentanediol (1,2-PD)and/or 1,2-hexanediol (1,2-HD) and the addition amount of the abovedescribed acetylene glycol-based surface active agent and/or theacetylene alcohol-based surface active agent is at least 0.5%, the inkjet recording ink set of the invention has a feature that the ratio thesurface active agent to the above-described 1,2-alkylene glycol is from1:0 to 1:10.

The 1,2-alkylene glycol, which gives a high effect by using as it is, is1,2-pentanediol and/or 1,2-hexanediol. The addition amount of1,2-pentanediol is preferably from 3 to 15%. When the addition amount isless than 3%, the effect of improving the permeability of the ink islow, and when the carbon number exceeds 15, the compound is reluctant touse for the water-soluble ink as in the invention since thewater-solubility of the compound is low. The addition amount of1,2-hexanediol is preferably from 0.5 to 10%. When the addition amountis less than 0.5%, the effect of improving the permeability of the inkis low, and when the carbon number exceeds 10, the compound is reluctantto use for the water-soluble ink as in the invention since thewater-solubility of the compound is low.

Also, the ink jet recording ink of the invention has a feature that itcontains from 0 to 5% by weight of an acetylene glycol surface activeagent.

By adding the acetylene glycol surface active agent to the ink, thequality of the prints can be more improved. The addition amount of thesurface active agent is from 0 to 5% by weight, and when the additionamount exceeds 5% by weight, the quality of the prints are not moreimproved corresponding to the excessive addition amount and on thecontrary, an evil effect of increasing the viscosity of the ink occurs.More preferred addition amount thereof is from 0.1 to 2% by weight. Asexamples of the acetylene glycol-based surface active agent, there areSurfynol series of Air Products and Chemicals Inc. (U.S.A.).

Furthermore, the ink jet recording ink of the invention has a featurethat it contains from 0 to 20% by weight of di(tri) ethylene glycolmonobutyl ether.

From the viewpoint of improving the printing quality, it is preferred toadd di(tri)ethylene glycol monobutyl ether. Di(tri)ethylene glycolmonobutyl ether is useful for improving the solubility of the acetyleneglycol-based surface active agent and for improving the printingquality, but when the addition amount exceeds 10 times, these effectsbecome the peak and thus such a large amount becomes hard to be used forink jet.

The ink jet recording inks of the invention contain, as the case may be,various additives such as a humectant, a dissolution aid, a penetrationcontrolling agent, a viscosity controlling agent, a pH controllingagent, a dissolution aid, an antioxidant, an antifungal agent, acorrosion preventing agent, a metal salt trapping agent, etc., for thepurposes of ensuring the stability of allowing to stand the ink, andattaining stable ejection of the ink from a ink ejection head, etc., andthe addition of these additives is included in the invention. Theexamples of them are shown below.

For restraining drying of the ink at the front of a nozzle, it ispreferred to add a glycol having a water solubility and examples of sucha glycol include ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, dipropylene glycol, tripropylene glycol, polyethyleneglycol having a molecular weight of not more than 2000, 1,3-propyleneglycol, isopropylene glycol, isobutylene glycol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, glycerol, mesoerythritol, andpentaerythritol.

Also, for restraining clogging a nozzle by drying the ink at the frontof the nozzle in the invention, various kinds of saccharide can be used.

As the usable saccharide, there are monosaccharides and polysaccharides,and practically, in addition of glucose, mannose, fructose, ribose,xylose, arabinose, lactose, galactose, aldonic acid, glucitose, maltose,cellobiose, sucrose, toleharose, maltotriose, etc., alginic acid and thesalts thereof, cyclodextrins, and celluloses. Also, the addition amountthereof is preferably at least 0.05% and not more than 30%. When theaddition amount is less than 0.05%, the effect of recovering thephenomenon of clogging a nozzle by drying the ink at the tip of thenozzle head is less, while the addition amount exceeds 30%, theviscosity of the ink is increased and proper printing cannot be carriedout.

The more preferred addition amount of glucose, mannose, fructose,ribose, xylose, arabinose, lactose, galactose, aldonic acid, glucitose,maltose, cellobiose, sucrose, toleharose, maltotriose, etc., asmonosaccharides and polysaccharide, which are general saccharide, isfrom 3 to 20%. It is necessary that the addition amount of alginic acidand the salts thereof, cyclodextrins, and celluloses is an extent thatthe viscosity of the ink added does not become too high.

As other additives, there are glycol ethers having a compatibility withwater and having a low solubility in water contained in the ink, andcompounds, which can be used for improving the solubility of the inkcomponents, and further improving the permeability of the ink to arecording medium (for example, papers), or for preventing clogging ofnozzle. These additives include alkyl alcohols having from 1 to 4 carbonatoms, such as ethanol, methanol, butanol, propanol, isopropanol, etc.;glycol ethers such as ethylene glycol methyl ether, ethylene glycolmonoethyl ether, ethylene glycol monobutyl ether, ethylene glycolmonomethyl ether acetate, diethylene glycol monomethyl ether, diethyleneglycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethyleneglycol mono-iso-propyl ether, diethylene glycol, mono-iso-propyl ether,ethylene glycol mono-n-butyl ether, diethylene glycol mono-n-butylether, triethylene glycol mono-n-butyl ether, ethylene glycolmono-t-butyl ether, diethylene glycol mono-t-butyl ether,1-methyl-1-methoxy butanol, propylene glycol monomethyl ether, propyleneglycol monoethyl ether, propylene glycol mono-t-butyl ether, propyleneglycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether,dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether,dipropylene glycol mono-n-propyl ether, dipropylene glycolmono-iso-propyl ether, propylene glycol mono-n-butyl ether, dipropyleneglycol mono-n-butyl ether, etc.; and formamide, acetamide, dimethylsulfoxide, sorbitol, sorbitan, acetin, diacetin, triacetin, sulfolane,etc. They can be appropriately selected and used.

Also, the ink in the invention can further contain other surface activeagent for controlling the permeability. As the surface active agentadded for the purpose, a surface active agent having a goodcompatibility with the inks shown in the examples of the invention ispreferred and in these surface active agents, a surface active agenthaving a high permeability and a good stability is preferred. As theexamples, there are amphoteric surface active agents, nonionic surfaceactive agents, etc.

The amphoteric surface active agents used in the invention includelauryldimethylaminoacetic acid betain,2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betain, coconut oilfatty acid amidopropyldimethylaminoacetuc acid betain, polyoctylpolyaminoethyl glycine, imidazoline derivatives, etc. The nonionicsurface active agents used in the invention include ether-based surfaceactive agents such as polyoxyethylene nonylphenyl ether, polyoxyethyleneoctylphenyl ether, polyoxyethylene dodecylphenyl ether, polyoxyethylenealkyl allyl ether, polyoxyethylene oleyl ether, polyoxyethylene laurylether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether, etc.;ester-based surface active agents such as polyoxyethylene oleic acid,polyoxyethylene oleic acid ester, polyoxyethylene distaric acid ester,sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitansesquioleate, polyoxyethylene monooleate, polyoxyethylene stearate,etc.; and fluorine-based surface active agents such as a fluorine alkylester, perfluoroalkyl carbonate, etc.

Also, as a pH controlling agent, a dissolution aid, or an antioxidant,there are amines such as diethanolamine, triethanolamine, propanolamine,morpholine, etc., and the modified products of them; inorganic saltssuch as potassium hydroxide, sodium hydroxide, lithium hydroxide, etc.;ammonium hydroxide, quaternary ammonium hydroxides (tetramethylammonium,etc.); carbonates such as potassium carbonate, sodium carbonate, lithiumcarbonate, etc.; or 1,3-dimethyl-2-imidazolidinone,N-methyl-2-pyrrolidone; ureas such as urea, thiourea, tetramethylurea,etc.; allophanates such as allophanate, methyl allophanate, etc.;biurets such as biuret, dimethyl biuret, etc.; and L-ascorbic acid andthe salts thereof, etc.

Also, commercially available antioxidants, ultraviolet absorbents, etc.,can be used. The examples thereof include Tinuvin 328, 900, 1130, 384,292, 123, 144, 622, and 770; and Irganox 1010, 1076, and 1035; MD1024,etc., manufactured by Ciba-Geigy Corporation, and the oxides oflanthanide.

Furthermore, the viscosity controlling agents used in the inventioninclude rosins, alginic acids, polyvinyl alcohol, hydroxypropylcellulose, carboxymethyl cellulose, hydroxyethyl cellulose methylcellulose, polyacrylates, polyvinyl pyrrolidone, gum arabic, starch,etc.

EXAMPLES

The present invention will be illustrated in greater detail withreference to the following Examples, but the invention should not beconstrued as being limited thereto.

(Production Examples of Colorant Enclosing Coloring Material WithPolymer Having Crosslinked Structure)

Production Example 1

(1-1) Synthesis of Polymer Having Crosslinking Reactive Group andHydrophilic Group:

A mixed liquid composed of 84 parts by weight of benzyl methacrylate, 85parts by weight of n-butyl acrylate, 35 parts by weight of2-hydroxyethyl methacrylate, 25 parts by weight of methacrylic acid, 13parts by weight of glycidyl methacrylate, and 20.0 parts by weight oft-hexylperoxy-2-ethylhexanate was prepared. Then, 300 parts by weight ofmethyl ethyl ketone was charged in a reaction vessel and after raisingthe temperature to 75° C. with stirring under a nitrogen seal, theabove-described mixed liquid was added dropwise thereto over a period of2 hours. After finishing the addition, the reaction was further carriedout for 20 hours at the same temperature and thereafter, methyl ethylketone was distilled off to obtain a polymer.

As the result of GPC, the weight average molecular weight of the polymerwas about 13000.

(1-2) Colorant 1-A:

Production of Colorant Enclosing Carbon Black With Polymer HavingCrosslinked Structure:

50 parts by weight of toluene was added to 6 parts by weight of thepolymer obtained in the above-described (1-1) to dissolve the polymertherein, and 20 parts by weight of carbon black (Raven C: manufacturedby Columbia Ribbon & Carbon Mfg. Co., Inc.) was added thereto. Afterdispersing it using a bead mill dispersing apparatus, the beads usedwere removed by filtration to obtain a liquid, and further 0.3 part byweight of para-methanediamine was added to the liquid obtained, followedby carrying out mixing and dissolution using a mixer. Then, whilecarrying out stirring and the irradiation of ultrasonic waves, 60 partsby weight of ion-exchanged water was added dropwise to the organicsolvent phase followed by carrying out an emulsification. Aftercompletely removing toluene from the emulsion at 60° C. under a reducedpressure, a crosslinking reaction was carried out at 80° C. over aperiod of 5 hours. Thereafter, the pH was adjusted to about 8 withpotassium hydroxide, and the reaction mixture was passed through afilter of 0.4 μm to obtain a dispersion of the desired colorant.

Measuring the particle sizes by Micro Track D. H. S. DPA (manufacturedby MOONTECH Corporation), the mean particle size was found to be 180 nm.In addition, the solid component concentration was 30.5%.

(1-3) Colorant 1-B

Production of Colorant Enclosing Yellow Pigment With Polymer HavingCrosslinked Structure

100 parts by weight of toluene was added to 30 parts by weight of thepolymer obtained by the above-described (1-1) to dissolve the polymertherein, and 20 parts by weight of C.I. Pigment Yellow 180 (manufacturedby Clariant K. K.) was added thereto. After dispersing the mixture usinga bead mill dispersing apparatus, the beads used were removed byfiltration to provide a liquid, and further 1.5 parts by weight ofpara-methanediamine was added to the liquid followed carrying out mixingand dissolution using a mixer. Then, while carrying out stirring and theirradiation of ultrasonic waves, 100 parts by weight of ion-exchangedwater was added dropwise to the organic solvent phase followed bycarrying out an emulsification. After completely removing toluene fromthe emulsion at 60° C. under a reduced pressure, the crosslinkingreaction was carried out at 80° C. over a period of 5 hours. Thereafter,the pH was adjusted to about 8 with potassium hydroxide, and thereaction mixture was passed through a filter of 0.4 μm to obtain adispersion of the desired colorant. Measuring the particle sizes byMicro Track D. H. S. DPA (manufactured by MOONTECH Corporation), themean particle size was found to be 180 nm. In addition, the solidcomponent concentration was 34%.

Using a part of the above-described dispersion, the liquid phase wasseparated from the colorant by a centrifugal separator, and as theresult of analyzing the liquid phase by GPC, the amount of water-solublesubstances originated in the polymer was 600 ppm.

(1-4) Colorant 1-C

Production of Colorant Enclosing Magenta Pigment With Polymer HavingCrosslinked Structure

100 parts by weight of toluene was added to 30 parts by weight of thepolymer obtained by the above-described (1-1), and 20 parts by weight ofC.I. Pigment Red 122 (manufactured by Clariant K. K.) was added thereto.After dispersing the mixture using a bead mill dispersing apparatus, thebeads used were removed by filtration to provide a liquid, and further1.5 parts by weight of para-methanediamine was added to the liquid,followed by carrying out mixing and dissolution using a mixer. Then,while carrying out stirring and the irradiation of ultrasonic waves, 100parts by weight of ion-exchanged water was added dropwise to the organicsolvent phase followed by carrying out an emulsification. Aftercompletely removing toluene from the emulsion at 60° C. under a reducedpressure, the crosslinking reaction was carried out at 80° C. over aperiod of 5 hours. Thereafter, the pH was adjusted to about 8 withpotassium hydroxide, and the reaction mixture was passed through afilter of 0.4 μm to obtain a dispersion of the desired colorant.Measuring the particle sizes by Micro Track D. H. S. DPA (manufacturedby MOONTECH Corporation), the mean particle size was found to be 150 nm.In addition, the solid component concentration was 34%.

Using a part of the above-described dispersion, the liquid phase wasseparated from the colorant by a centrifugal separator, and as theresult of analyzing the liquid phase by GPC, the amount of water-solublesubstances originated in the polymer was 600 ppm.

(1-5) Colorant 1-D:

Production of Colorant Enclosing Cyan Pigment With Polymer HavingCrosslinked Structure:

50 parts by weight of toluene was added to 6 parts by weight of thepolymer obtained by the above-described (1-1), and 20 parts by weight ofC.I. Pigment Blue 15:3 (manufactured by Clariant K. K.) was addedthereto. After dispersing the mixture using a bead mill dispersingapparatus, the beads used were removed by filtration to provide aliquid, and further 0.3 part by weight of para-methanediamine was addedto the liquid, followed by carrying out mixing and dissolution using amixer. Then, while carrying out stirring and the irradiation ofultrasonic waves, 60 parts by weight of ion-exchanged water was addeddropwise to the organic solvent phase followed by carrying out anemulsification. After completely removing toluene from the emulsion at60° C. under a reduced pressure, the crosslinking reaction was carriedout at 80° C. over a period of 5 hours. Thereafter, the pH was adjustedto about 8 with potassium hydroxide, and the reaction mixture was passedthrough a filter of 0.4 μm to obtain a dispersion of the desiredcolorant.

Measuring the particle sizes by Micro Track D. H. S. DPA (manufacturedby MOONTECH Corporation), the mean particle size was found to be 180 nm.In addition, the solid component concentration was 30.5%.

Production Example 2

(2-1) Synthesis of Polymer Having Crosslinking Reactive Group andHydrophilic Group:

A mixed liquid composed of 84 parts by weight of benzyl methacrylate, 85parts by weight of n-butyl acrylate, 35 parts by weight of2-hydroxyethyl methacrylate, 25 parts by weight of methacrylic acid, and20.0 parts by weight of t-hexylperoxy-2-ethylhexanate was prepared.Then, 300 parts by weight of methyl ethyl ketone was charged in areaction vessel and after raising the temperature to 75° C. withstirring under a nitrogen seal, the above-described mixed liquid wasadded dropwise thereto over a period of 2 hours. After finishing theaddition, the reaction was further carried out for 20 hours at the sametemperature to obtain a solution of a polymer having a number averagemolecular weight of 13,000. To the polymer solution were added 5 partsby weight of 2-methacryloyloxyethyl isocyanate (Karenz MOI, manufacturedby SHOWA DENKO K. K.), 0.1 part by weight of dibutyltin laurate, andfurther 200 ppm of hydroquinone, and the reaction was carried out at 70°C. for 5 hours by heating again to obtain a solution of a polymer havingan unsaturated hydrocarbon group as a crosslinking reactive group.

(2-2) Colorant 2-A

Production of Colorant Enclosing Carbon Black With Polymer HavingCrosslinked Structure:

30 parts by weight of toluene was added to 6 parts by weight of thepolymer obtained in the above-described (2-1) to dissolve the polymertherein, and 20 parts by weight of carbon black (Raven C: manufacturedby Columbia Ribbon & Carbon Mfg. Co., Inc.) was added thereto. Afterdispersing it using a bead mill dispersing apparatus, the beads usedwere removed by filtration to obtain a liquid, and further 0.3 part byweight of diethylene glycol was added to the liquid obtained, followedby mixing and dissolution using a mixer. Then, while applying stirringand the irradiation of ultrasonic waves, 60 parts by weight ofion-exchanged water having dissolved therein 1% by weight of potassiumpersulfate as a polymerization initiator was added dropwise to theorganic solvent phase followed by carrying out an emulsification. Theemulsion was subjected to a crosslinking reaction at 75° C. for 10 hoursand toluene was completely removed from the emulsion at 60° C. under areduced pressure. Thereafter, the pH was adjusted to about 8 withpotassium hydroxide, and the reaction mixture was passed through afilter of 0.4 μm to obtain a dispersion of the desired colorant.

Measuring the particle sizes by Micro Track D. H. S. DPA (manufacturedby MOONTECH Corporation), the mean particle size was found to be 180 nm.In addition, the solid component concentration was 30.5%.

(2-3) Colorant 2-B

Production of Colorant Enclosing Yellow Pigment With Polymer HavingCrosslinked Structure:

50 parts by weight of toluene was added to 30 parts by weight of thepolymer obtained by the above-described (2-1) to dissolve the polymertherein, and 20 parts by weight of C.I. Pigment Yellow 150 was addedthereto. After dispersing the mixture using a bead mill dispersingapparatus, the beads used were removed by filtration to provide aliquid, and further 0.3 parts by weight of diethylene glycol was addedto the liquid, followed by carrying out mixing and dissolution using amixer. Then, while applying stirring and the irradiation of ultrasonicwaves, 60 parts by weight of ion-exchanged water having dissolvedtherein 1% by weight of potassium persulfate as a polymerizationinitiator was added dropwise to the organic solvent phase followed bycarrying out an emulsification. The emulsion was subjected to acrosslinking reaction at 75° C. for 10 hours and toluene was completelyremoved from the emulsion at 60° C. under a reduced pressure.Thereafter, the pH was adjusted to about 8 with potassium hydroxide, andthe reaction mixture was passed through a filter of 0.4 μm to obtain adispersion of the desired colorant.

Measuring the particle sizes by Micro Track D. H. S. DPA (manufacturedby MOONTECH Corporation), the mean particle size was found to be 180 nm.In addition, the solid component concentration was 30.5%.

(2-4) Colorant 2-C

Production of Colorant Enclosing Magenta Pigment With Polymer HavingCrosslinked Structure:

50 parts by weight of toluene was added to 30 parts by weight of thepolymer obtained by the above-described (2-1) to dissolve the polymertherein, and 20 parts by weight of C.I. Pigment Red 122 was addedthereto. After dispersing the mixture using a bead mill dispersingapparatus, the beads used were removed by filtration to provide aliquid, and further 0.3 part by weight of diethylene glycoldimethacrylate was added to the liquid, followed by carrying out mixingand dissolution using a mixer. Then, while applying stirring and theirradiation of ultrasonic waves, 60 parts by weight of ion-exchangedwater having dissolved therein 1% by weight of potassium persulfate as apolymerization initiator was added dropwise to the organic solvent phasefollowed by carrying out an emulsification. The emulsion was subjectedto a crosslinking reaction at 75° C. for 10 hours and toluene wascompletely removed from the emulsion at 60° C. under a reduced pressure.Thereafter, the pH was adjusted to about 8 with potassium hydroxide, andthe reaction mixture was passed through a filter of 0.4 μm to obtain adispersion of the desired colorant.

Measuring the particle sizes by Micro Track D. H. S. DPA (manufacturedby MOONTECH Corporation), the mean particle size was found to be 180 nm.In addition, the solid component concentration was 30.5%.

(2-5) Colorant 2-D

Production of Colorant Enclosing Cyan Pigment With Polymer HavingCrosslinked Structure:

50 parts by weight of toluene was added to 30 parts by weight of thepolymer obtained by the above-described (2-1) to dissolve the polymertherein, and 20 parts by weight of C.I. Pigment Blue 15:3 was addedthereto. After dispersing the mixture using a bead mill dispersingapparatus, the beads used were removed by filtration to provide aliquid, and further 30 parts by weight of diethylene glycoldimethacrylate was added to the liquid, followed by carrying out mixingand dissolution using a mixer. Then, while applying stirring and theirradiation of ultrasonic waves, 60 parts by weight of ion-exchangedwater having dissolved therein 1% by weight of potassium persulfate as apolymerization initiator was added dropwise to the organic solvent phasefollowed by carrying out an emulsification. The emulsion was subjectedto a crosslinking reaction at 75° C. for 10 hours and toluene wascompletely removed from the emulsion at 60° C. under a reduced pressure.Thereafter, the pH was adjusted to about 8 with potassium hydroxide, andthe reaction mixture was passed through a filter of 0.4 μm to obtain adispersion of the desired colorant.

Measuring the particle sizes were measured by Micro Track D. H. S. DPA(manufactured by MOONTECH Corporation), the mean particle size was foundto be 160 nm.

Production Example 3

In a preferred embodiment of the invention, each of the colorants in theinvention is obtained by dispersing well the pigment in an aqueousorganic solvent and/or water using a dispersing agent having apolymerizable group and thereafter, carrying out the polymerizationreaction of the dispersion together with the dispersing agent having apolymerizable group and a crosslinkable monomer under the existence of apolymerization initiator in a reaction vessel equipped with a stirrer, athermometer, a temperature controller, a reflux condenser and a droppingfunnel.

In the production example 3, “colorants each enclosing a coloringmaterial with a polymer having a crosslinked structure” were obtained bythe following production methods.

(3-1) Colorant 3-A

Production of Colorant Enclosing Carbon Black With Polymer HavingCrosslinked Structure:

The colorant 3-A was prepared by the method according to Example 1described in Japanese Patent Laid-Open No. 316909/1998. That is, in areaction vessel equipped with a ultrasonic generator, a stirrer, atemperature controller, a reflux condenser and a dropping funnel, 50parts by weight of carbon black (Raven C: manufactured by ColumbiaRibbon & Carbon Mfg. Co., Inc.) and 30 parts by weight of apolymerizable surface active agent SE-10N shown by the formula (I)(manufactured by ASAHI DENKA KOGYO K. K.) were added into 800 parts byweight of water, and they were dispersed by applying ultrasonic wavesfor 4 hours. Then, 16 parts by weight of acrylonitrile, 2.4 parts byweight of divinylbenzene, and 0.5 part by weight of potassium persulfatewere further added thereto and a polymerization reaction was carried outat 60° C. for 48 hours. Thereafter, the pH was adjusted to about 8 withpotassium hydroxide and the reaction mixture was filtered by a filter of0.4 μm to remove coarse particles, whereby the desired colorant wasobtained in the form of a dispersion.

(3-2) Colorant 3-B:

Production of Colorant Enclosing Yellow Pigment With Polymer HavingCrosslinked Structure:

By following the same procedure as above except for using apolymerizable surface active agent Aquaron HS-10 shown by the formula(II) in place of the polymerizable surface active agent Adekarea SoapSE-10N (manufactured by ASAHI DENKA KOGYO K. K.) shown by the formula(I) used in the above-described (3-1) and using C.I. Pigment Yellow 128as the coloring material, a desired colorant was obtained in the form ofa dispersion.

(3-3) Colorant 3-C

Production of Colorant Enclosing Magenta Pigment With Polymer HavingCrosslinked Structure:

By following the same procedure as the production of the above-described(3-1) except that C.I. Pigment Red 122 was used as the coloringmaterial, a desired colorant was obtained in the form of a dispersion.

(3-4) Colorant 3-D

Production of Colorant Enclosing Cyan Pigment With Polymer HavingCrosslinked Structure:

By following the same procedure as the production of the above-described(3-1) except that C.I. Pigment Blue 15:3 was used as the coloringmaterial, a desired colorant was obtained in the form of dispersion.

(3-5): Colorant 3-E

Production of Colorant Enclosing Orange Pigment With Polymer HavingCrosslinked Structure:

In a reaction vessel equipped with a ultrasonic generator, a stirrer, atemperature controller, a reflux condenser and a dropping funnel, 50parts by weight of C.I. Pigment Orange 36 and 30 parts by weight of apolymerizable surface active agent SE-10N shown by the formula (I)(manufactured by ASAHI DENKA KOGYO K. K.) were added into 800 parts byweight of water, and they were dispersed by applying ultrasonic wavesfor 4 hours. Then, 16 parts by weight of acrylonitrile, 5 parts byweight of diallyl isocyanate, and 0.5 part by weight of potassiumpersulfate were further added thereto and a polymerization reaction wascarried out at 60° C. for 48 hours. Thereafter, the pH was adjusted toabout 8 with potassium hydroxide and the reaction mixture was filteredby a filter of 0.4 μm to remove coarse particles, whereby a desiredcolorant was obtained in the form of dispersion.

(3-6) Colorant F

Production of Colorant Enclosing Green Pigment With Polymer HavingCrosslinked Structure:

In a reaction vessel equipped with a ultrasonic generator, a stirrer, atemperature controller, a reflux condenser and a dropping funnel, 50parts by weight of C.I. Pigment Green 36 and 30 parts by weight of apolymerizable surface active agent SE-10N shown by the formula (I)(manufactured by ASAHI DENKA KOGYO K. K.) were added into 800 parts byweight of water, and they were dispersed by applying ultrasonic wavesfor 4 hours. Then, 16 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 3 parts by weight of acrylonitrile, 5 parts by weight ofdivinylbenzene, and 0.5 part by weight of potassium persulfate werefurther added to the dispersion and a polymerization reaction wascarried out at 60° C. for 48 hours. Thereafter, the pH was adjusted toabout 8 with potassium hydroxide and the reaction mixture was filteredby a filter of 0.4 μm to remove coarse particles, whereby a desiredcolorant was obtained in the form of dispersion.

(Production Examples of Colorants Enclosing Coloring Material WithPolymer (Copolymer) of Dispersing Agent Having Polymerizable Group andMonomer (Copolymerizable Monomer))

Production Example 4

Example 4 includes production examples of producing colorants eachenclosing a pigment with a polymer without having a crosslinkedstructure (a polymer (copolymer) of a dispersing agent having apolymerizable group and a monomer (copolymerizable monomer)).

That is, the colorant is obtained by dispersing well the pigment in anaqueous organic solvent and/or water using the dispersing agent having apolymerizable group and thereafter, carrying out the polymerizationreaction of the dispersion together with the dispersing agent having apolymerizable group alone or with other copolymerizable monomer underthe existence of a polymerization initiator in a reaction vesselequipped with a stirrer, a thermometer, a temperature controller, areflux condenser and a dropping apparatus at a definite reactiontemperature for a definite reaction time.

The mean particle size of each colorant was measured by the laserDoppler system, particle distribution measurement machine, Microtrac UPA150, manufactured by Leeds & Northrup Co. Also, the glass transitiontemperature of the polymer of the colorant was measured by a heatscanning type calorimeter (differential scanning calorimeter: DSC)manufactured by Seiko Denshi K. K., and obtained by the above-describedmethod.

(4-1) Colorant 4-A

Production of Black Colorant

The colorant 4-A was produced by the method same as Example 1 ofJapanese Patent Laid-Open No. 316909/1998. That is, 100 parts by weightof carbon black (Raven C: manufactured by Columbia Ribbon & Carbon Mfg.Co., Inc.) and 60 parts by weight of the polymerizable surface activeagent, Adekarea Soap SE-10N shown by the formula (IV) manufactured byASAHI DENKA KOGYO K. K.) were added into 250 parts by weight of waterfollowed by irradiating ultrasonic waves, and the mixture was furthersubjected to a dispersing treatment by a sand mill (manufactured byYasukawa Seisakusho K. K.) for about 2 hours. This carbon black wasdispersed with the polymerizable surface-active agent, and thedispersion thus obtained was placed in a reaction vessel equipped with aultrasonic generator, a stirrer, a temperature controller, a refluxcondenser and a dropping funnel. Then, an emulsion was previouslyprepared by mixing 30 parts by weight of acrylonitrile, 9 parts byweight of styrene, 51 parts by weight of n-butyl acrylate, 10 parts byweight of methacrylic acid, 10 parts by weight of the above-describedpolymerizable surface active agent, 1 part by weight of potassiumpersulfate and 100 parts by weight of water, and the emulsion wasgradually added dropwise to the reaction vessel using the droppingfunnel. After finishing the addition, the polymerization reaction wascarried out at 60° C. for 48 hours. The dispersion of the colorantobtained was neutralized with potassium hydroxide to adjust the pH toabout 8 and the dispersion was filtered with the filter of 0.4 μm toremove coarse particles, whereby a dispersion of a desired colorant 4-Awas obtained.

Measuring the mean particle size of the colorant by the laser Dopplersystem, particle measurement machine, Microtrac UPA 150 (manufactured byLeeds & Northrup Co.), the mean particle size was found to be 105 nm.Also, measuring the glass transition temperature of the colorant 4-A bya heat scanning type calorimeter (differential scanning calorimeter: DSC200) manufactured by Seiko Denshi K. K., the glass transitiontemperature of the colorant was found to be 10° C.

(4-2) Colorant 4-B

Production of Yellow Colorant

By the same manner as the case of producing the colorant 4-A except thatC.I. Pigment Yellow 180 (diketopyrrolopyrrole: manufactured by ClariantCo.) was used in place of the carbon black pigment, a dispersion of adesired colorant 4-B was obtained.

Measuring the mean particle size of the colorant by the laser Dopplersystem, particle measurement machine, Microtrac UPA 150 (manufactured byLeeds & Northrup Co.), the mean particle size was found to be 80 nm.Also, measuring the glass transition temperature of the colorant 4-B bya heat scanning type calorimeter (differential scanning calorimeter: DSC200) manufactured by Seiko Denshi K. K., the glass transitiontemperature of the colorant was found to be 10° C.

(4-3) Colorant 4-C

Production of Magenta Colorant

By the same manner as the case of producing the colorant 4-A except thatC.I. Pigment Red 122 (dimethyl quinacridone pigment: manufactured byClariant Co.) was used in place of the carbon black pigment, adispersion of a desired colorant 4-C was obtained.

Measuring the mean particle size of the colorant by the laser Dopplersystem, particle measurement machine, Microtrac UPA 150 (manufactured byLeeds & Northrup Co.), the mean particle size was found to be 90 nm.Also, measuring the glass transition temperature of the colorant 4-C bya heat scanning type calorimeter (differential scanning calorimeter: DSC200) manufactured by Seiko Denshi K. K., the glass transitiontemperature of the colorant was found to be 10° C.

(4-4) Colorant 4-D

Production of Cyan Colorant

By the same manner as the case of producing the colorant 4-A except thatC.I. Pigment Blue 15:3 (copper phthalocyanine pigment: manufactured byClariant Co.) was used in place of the carbon black pigment, adispersion of a desired colorant 4-D was obtained.

Measuring the mean particle size of the colorant by the laser Dopplersystem, particle measurement machine, Microtrac UPA 150 (manufactured byLeeds & Northrup Co.), the mean particle size was found to be 85 nm.Also, measuring the glass transition temperature of the colorant 4-D bya heat scanning type calorimeter (differential scanning calorimeter: DSC200) manufactured by Seiko Denshi K. K., the glass transitiontemperature of the colorant was found to be 10° C.

(Preparations of the Inks of Examples 1 to 3 of the Invention and theInk of Comparative Example 1)

Each of the inks having the compositions shown in Table 1 to Table 3below was prepared by the following methods.

An aqueous medium not including the colorant obtained as described abovewas previously prepared, and the aqueous medium was gradually addeddropwise to the dispersion of the colorant obtained as described abovein a stirred state, followed by sufficiently stirring. The mixture wasfiltered by a membrane filter of 5 μm to obtain each ink.

In Table 1 to Table 3 described below, Olfin E1010 (manufactured byNisshin Kagaku Kogyo K. K.) is an acetylene glycol-based surface activeagent. Also, in the tables, Bk represents black, Y: yellow, M: magenta,C: cyan, Or: orange, and Gr: green.

TABLE 1 Example 1 Example 2 Bk Y M C Bk Y M C Colorant 1-A 5.0 Colorant1-B 5.0 Colorant 1-C 5.0 Colorant 1-D 5.0 Colorant 2-A 5.0 Colorant 2-B5.0 Colorant 2-C 5.0 Colorant 2-D 5.0 Olfin E1010 1.0 1.0 1.0 1.0Diethylene 5.0 5.0 5.0 5.0 glycol monobutyl ether Triethylene 5.0 5.05.0 5.0 glycol monobutyl ether Propylene glycol monobutyl etherDipropylene 2.0 2.0 2.0 2.0 glycol monobutyl ether 1,2-Pentane- 5.0 5.05.0 5.0 diol 1,2-Hexane- 5.0 5.0 5.0 5.0 diol Glycerol 10.0  10.0  10.0 10.0  10.0  10.0  10.0  10.0  Triethanol- 0.5 0.5 0.5 0.5 0.5 0.5 0.50.5 amine Potassium 0.1 0.1 0.1 0.1 hydroxide Ion exchanged bal. bal.bal. bal. bal. bal. bal. bal. water

TABLE 2 Example 3 Bk Y M C Or Gr Colorant 3-A 8.0 Colorant 3-B 8.0Colorant 3-C 8.0 Colorant 3-D 8.0 Colorant 3-E 8.0 Colorant 3-F 8.0Olfin E1010 1.0 1.0 1.0 1.0 1.0 1.0 Diethylene glycol 5.0 5.0 5.0 5.05.0 5.0 monobutyl ether Triethylene glycol monobutyl ether Propyleneglycol 2.0 2.0 2.0 2.0 2.0 2.0 monobutyl ether Dipropylene glycolmonobutyl ether 1,2-Pentanediol 1,2-Hexanediol 5.0 5.0 5.0 5.0 5.0 5.0Glycerol 10.0  10.0  10.0  10.0  10.0  10.0  Triethanolamine 0.5 0.5 0.50.5 0.5 0.5 Potassium hydroxide 0.1 0.1 0.1 0.1 0.1 0.1 Ion exchangedwater bal. bal. bal. bal. bal. bal.

TABLE 3 Comparative Example 1 Bk Y M C Or Gr Bk Dispersion 4.0 (carbonblack) Y Dispersion 4.0 (C.I. Pigment Yellow 151) M Dispersion 4.0 (C.I.Pigment Red 160) C Dispersion 4.0 (C.I. Pigment Blue 60) Or Dispersion4.0 (C.I. Pigment Orange 20) Gr Dispersion 4.0 (C.I. Pigment Green 8)Olfin E1010 1.0 1.0 1.0 1.0 1.0 1.0 Diethylene glycol 5.0 5.0 5.0 5.05.0 5.0 monobutyl ether Triethylene glycol monobutyl ether Propyleneglycol monobutyl ether Dipropylene glycol 2.0 2.0 2.0 2.0 2.0 2.0monobutyl ether 1,2-Pentanediol 1,2-Hexanediol 5.0 5.0 5.0 5.0 5.0 5.0Glycerol 10.0  10.0  10.0  10.0  10.0  10.0  Triethanolamine 0.5 0.5 0.50.5 0.5 0.5 Potassium hydroxide 0.1 0.1 0.1 0.1 0.1 0.1 Ion exchangedwater bal. bal. bal. bal. bal. bal.

Ink Sets of Examples 1 to 3 and Ink Set of Comparative Example 1

The ink sets of Examples 1 to 3 and Comparative Example 1 each comprisesa combination of “Bk, Y, M and C” or “Bk, Y, M, C, Or and Gr” shown inTables 1 to 3 described above.

In addition, the “Bk dispersion” in Comparative Example 3 shown in Table3 was prepared by dispersing 40% by weight of carbon black (Raven C:manufactured by Columbia Ribbon & Carbon Mfg. Co., Inc.), which is C.I.Pigment Black 7), 3% by weight of a general acrylic dispersing agent,and 20% by weight of water in a sand mill (manufactured by YasukawaSeisakusho K. K.). About other colors, “Y dispersion”, “M dispersion”,“C dispersion”, “Or dispersion”, and “Gr dispersion” were similarlyprepared. The coloring materials used are shown below.

Y: C.I. Pigment Yellow 151 M: C.I. Pigment Red 160 C: C.I. Pigment Blue60 Or: C.I. Pigment Orange 20 Gr: C.I. Pigment Green 8

(Evaluation of Inks)

<Evaluation 1: Ejection Stability>

About each ink, letters were continuously printed using an ink jetprinter, MJ-930C (manufactured by Seiko Epson Corporation) on a P-paperof Fuji Xerox Co., Ltd., and the states of the prints, such as a dotdeletion, the displacement in the ink-landing positions, etc., werevisually observed, and they were evaluated in accordance with thefollowing criteria.

“Evaluation Criteria”

A: Even after printing 1000 prints, there are no dot deletion, nodisplacement in the ink-landing positions, etc.

B: After printing 100 prints, there are no dot deletion, no displacementin the ink-landing positions, etc.

C: Before printing 100 prints, the occurrences of the dot deletion andthe displacement in the ink-landing positions are observed.

The results are shown in Table 4 below.

<Evaluation 2: Dispersion Stability>

Each ink was stored for one week at 60° C., the initial viscosity of inkand the viscosity of the ink after one week were measured, and the ratioof the viscosity after one week to the initial viscosity was determined.When the viscosity ratio was 1, the ink was evaluated to be stable. Theresults are shown in Table 4.

TABLE 4 Bk Y M C Or Gr E.S. D.S. E.S. D.S. E.S. D.S. E.S. D.S. E.S. D.S.E.S. D.S. Ex.1 B 1.0 B 1.0 B 1.0 B 1.0 — — Ex.2 B 1.0 B 1.0 B 1.0 B 1.0— — Ex.3 A 1.0 A 1.0 A 1.0 A 1.0 A 1.0 A 1.0 CE 1 C 1.8 C 3.1 C 2.0 C1.3 C 1.5 C 1.3 In Table 4: E.S.: Ejection stability D.S.: Dispersionstability Ex.: Example CE: Comparative Example

<Evaluation 3: Surface Tension>

The surface tension of each ink was measured by an automatictensiometer, Type CBVP-Z, manufactured by Kyowa Kaimen Kagaku K. K. Theresults are shown in Table 5 below.

TABLE 5 Surface tension of ink (unit: mN/m) Bk Y M C Or Gr Example 131.3 30.5 32.7 31.0 — — Example 2 31.3 29.8 31.3 29.9 — — Example 3 29.529.4 32.2 31.4 28.6 28.8 C. Example 1 30.2 29.9 31.2 28.5 30.9 29.4 C.Example: Comparative Example

(Color Evaluation Tests)

<Evaluation 4: Color Developing Property of Red Color>

For printing a red color with the ink set of four colors and the ink setof six colors using PM-770C and using each ink set, a driver wasprepared for the evaluation, and printing was carried out. Thesaturation of the red color obtained by each ink set was measured.

The evaluation was made in accordance with the criteria shown below.Also, printing was applied onto the evaluation papers shown below. Theresults of the evaluations are shown in Table 6.

“Evaluation Criteria”

A: Saturation is at least 80.

B: Saturation is at least 70 and lower than 80.

C: Saturation is at least 60 and lower than 70.

D: Saturation is lower than 60.

“Evaluation Papers”

Paper 1: Xerox 4024 paper (manufactured by Fuji Xerox Co., Ltd.)

Paper 2: High-quality plain paper (manufactured by Seiko EpsonCorporation)

Paper 3: Photo-print paper 2

Paper 4: Super fine paper

<Evaluation 5: Color Developing Property of Green Color>

For printing a green color with the ink set of four colors and the inkset of six colors using PM-770C and using each ink set, a driver wasprepared for the evaluation, and printing was carried out. Thesaturation of the green color obtained by each ink set was measured.

The evaluation was made in accordance with the criteria shown below.Printing was carried out using the above-described evaluation papers“Paper 1 to Paper 4”. The results of the evaluation are shown in Table6.

“Evaluation Criteria”

A: Saturation is at least 80.

B: Saturation is at least 70 and lower than 80.

C: Saturation is at least 60 and lower than 70.

D: Saturation is lower than 60.

<Evaluation 6: Color Developing Property of Orange Color>

For printing an orange color with the ink set of four colors and the inkset of six colors using PM-770C and using each ink set, a driver wasprepared for the evaluation, and printing was carried out. Thesaturation of the orange color obtained by each ink set was measured.

The evaluation was made in accordance with the criteria shown below.Printing was carried out using the above-described evaluation papers“Paper 1 to Paper 4”. The results of the evaluation are shown in Table6.

“Evaluation Criteria”

A: Saturation is at least 80.

B: Saturation is at least 70 and lower than 80.

C: Saturation is at least 60 and lower than 70.

D: Saturation is lower than 60.

TABLE 6 COLOR EVALUATION Color developing Color developing Colordeveloping property of red property of green property of color colororange color Evaluation paper P.1 P.2 P.3 P.4 P.1 P.2 P.3 P.4 P.1 P.2P.3 P.4 Ex. 1 B B A A B B A B B B A B Ex. 2 B B A A B B A B B B A B Ex.3 B B A A B A A A B A A A Comp. Ex. 1 D D B C D D B C D D B C P.1 toP.4: Paper 1 to Paper 4

(Preparations of the Inks of Examples 4 to 6 of the Invention and theInk of Comparative Example 2)

The inks having the compositions shown in Table 7 to Table 10 shownbelow were prepared by the following procedures similarly to thepreparations of the inks of above-described Examples 1 to 3.

An aqueous medium not including the colorant obtained as described abovewas previously prepared, and the aqueous medium was gradually addeddropwise to the dispersion of the colorant obtained as described abovein a stirred state and the mixture was sufficiently stirred. The mixturewas filtered by a membrane filter of 5 μm to obtain the each ink.

In Table 7 to Table 10 shown below, Olfin E1010 (manufactured by NisshinKagaku Kogyo K. K.) is an acetylene glycol-based surface active agent.Also, in the tables, Bk represents black, LBk: light black, Y: yellow,M: magenta, LM: light magenta. C: cyan, and LC: light cyan.

TABLE 7 Example 4 Bk Y M LM C LC Colorant 1-A 8.0 Colorant 1-B 8.0Colorant 1-C 8.0 2.0 Colorant 1-D 8.0 2.0 Olfin E1010 1.0 1.0 1.0 1.01.0 1.0 Diethylene glycol monobutyl 5.0 5.0 5.0 5.0 5.0 5.0 etherTriethylene glycol monobutyl ether Propylene glycol monobutyl 2.0 2.02.0 2.0 2.0 2.0 ether Dipropylene glycol monobutyl ether 1,2-Pentanediol1,2-Hexanediol 5.0 5.0 5.0 5.0 5.0 5.0 Glycerol 10.0  10.0  10.0  10.0 10.0  10.0  Triethanolamine 0.5 0.5 0.5 0.5 0.5 0.5 Potassium hydroxide0.1 0.1 0.1 0.1 0.1 0.1 Ion exchanged water bal. bal. bal. bal. bal.bal.

TABLE 8 Example 5 Bk LBk Y M LM C LC Colorant 2-A 8.0 4.0 Colorant 2-B8.0 Colorant 2-C 8.0 1.5 Colorant 2-D 5.0  1.25 Olfin E1010 1.0 1.0 1.01.0 1.0 1.0 1.0 Diethylene glycol 5.0 5.0 5.0 5.0 5.0 5.0 5.0 monobutylether Triethylene glycol monobutyl ether Propylene glycol 2.0 2.0 2.02.0 2.0 2.0 2.0 monobutyl ether Dipropylene glycol monobutyl ether1,2-Pentanediol 1,2-Hexanediol 5.0 5.0 5.0 5.0 5.0 5.0 5.0 Glycerol10.0  10.0  10.0  10.0  10.0  10.0  10.0  Triethanolamine 0.5 0.5 0.50.5 0.5 0.5 0.5 Potassium hydroxide 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Ionexchanged water bal. bal. bal. bal. bal. bal. bal.

TABLE 9 Example 6 Bk Y N LM C LC Colorant 3-A 8.0 Colorant 3-B 8.0Colorant 3-C 8.0 2.0 Colorant 3-D 6.0 1.5 Olfin E1010 1.0 1.0 1.0 1.01.0 1.0 Diethylene glycol monobutyl 5.0 5.0 5.0 5.0 5.0 5.0 etherTriethylene glycol monobutyl ether Propylene glycol monobutyl 2.0 2.02.0 2.0 2.0 2.0 ether Dipropylene glycol monobutyl ether 1,2-Pentanediol1,2-Hexanediol 5.0 5.0 5.0 5.0 5.0 5.0 Glycerol 10.0  10.0  10.0  10.0 10.0  10.0  Triethanolamine 0.5 0.5 0.5 0.5 0.5 0.5 Potassium hydroxide0.1 0.1 0.1 0.1 0.1 0.1 Ion exchanged water bal. bal. bal. bal. bal.bal.

TABLE 10 Comparative Example 2 Bk Y M LM C LC Bk Dispersion (carbonblack) 4.0 Y Dispersion 4.0 (C.I. Pigment Yellow 151) M Dispersion 4.0(C.I. Pigment Red 160) C Dispersion 4.0 (C.I. Pigment Blue 60) OlfinE1010 1.0 1.0 1.0 1.0 1.0 1.0 Diethylene glycol monobutyl 5.0 5.0 5.05.0 5.0 5.0 ether Triethylene glycol monobutyl ether Propylene glycolmonobutyl ether Dipropylene glycol monobutyl 2.0 2.0 2.0 2.0 2.0 2.0ether 1,2-Pentanediol 1,2-Hexanediol 5.0 5.0 5.0 5.0 5.0 5.0 Glycerol10.0  10.0  10.0  10.0  10.0  10.0  Triethanolamine 0.5 0.5 0.5 0.5 0.50.5 Potassium hydroxide 0.1 0.1 0.1 0.1 0.1 0.1 Ion exchanged water bal.bal. bal. bal. bal. bal.

(Ink Sets of Examples 4 to 6 and Ink set of Comparative Example 2)

The ink sets of Examples 4 to 6 of the invention and the ink set ofComparative Example 2 comprise a combination of “Bk, Y, M, LM, C and LC”or “Bk, LBk, Y, M, LM, C and LC” as shown in Tables 7 to 10.

In addition, the “Bk dispersion” of Comparative Example 2 in Table 10was prepared by dispersing 4.0% by weight of carbon black (Raven C:manufactured by Columbia Ribbon & Carbon Mfg. Co., Inc.), 3% by weightof a general acrylic dispersing agent, and 20% by weight of water in asand mill (Yasukawa Seisakusho K. K.). In regard to other colors, the “Ydispersion”, “M dispersion”, and “C dispersion” were similarly prepared.

The Coloring Materials Used are Shown Below.

Y: C.I. Pigment Yellow 151

M: C.I. Pigment Red 160

C: C.I. Pigment Blue 60

(Evaluation of Inks)

<Evaluation 7: Ejection Stability>

<Evaluation 8: Dispersion Stability>

With respect to each of the inks of Examples 4 to 6 and ComparativeExample 2, the evaluations of the “Evaluation 7: Ejection stability” and“Evaluation 8: Dispersion stability” were carried out by the sameconditions as “Evaluations 1 and 2”, respectively. The results are shownin Table 11.

TABLE 11 Bk LBk Y M LM C LC E.S. D.S. E.S. D.S. E.S. D.S. E.S. D.S. E.S.D.S. E.S. D.S. E.S. D.S. Ex. 4 A 1.0 — A 1.0 A 1.0 A 1.0 A 1.0 A 1.0 Ex.5 A 1.0 A 1.0 A 1.0 A 1.0 A 1.0 A 1.0 A 1.0 Ex. 6 A 1.0 — A 1.0 A 1.0 A1.0 A 1.0 A 1.0 Comp. Ex. 2 C 1.8 — C 3.1 C 2.0 C 1.3 C 1.5 C 1.3 E.S.:Ejection stability, D.S.: Dispersion stability

<Evaluation 9: Surface Tension>

The surface tension of each ink was measured by an automatictensiometer, Type CBVP-Z, manufactured by Kyowa Kaimen Kagaku K. K. Theresults are shown in Table 12 below.

TABLE 12 Surface tension of each ink (unit: mN/m) Bk LBk Y M LM C LCExample 4 29.5 — 29.4 32.2 32.4 28.6 28.9 Example 5 29.5 29.4 32.2 31.431.7 30.5 30.9 Example 6 29.5 — 29.4 32.2 32.3 28.6 28.8 Comparative30.2 — 29.9 31.2 31.6 29.9 29.4 Example 2

<Evaluation 10: Color Developing Property>

PM-770C was upgraded, using each ink set, an upgraded driver wasprepared for the evaluation, and 100% duty of Y, M, C, R, G and Bk wasprinted. The saturation of each of Y, M, C, R, G and Bk obtained wasmeasured.

The evaluation was made in accordance with the criteria shown below.Printing was carried out on the evaluation papers shown below. Theresults are shown in Table 13.

“Evaluation Criteria”

A: Saturation is at least 80.

B: Saturation is at least 70 and lower than 80.

C: Saturation is at least 60 and lower than 70.

D: Saturation is lower than 60.

“Evaluation Papers”

Paper 5: Xerox 4024 paper (Fuji Xerox Co., Ltd.)

Paper 6: High-quality plain paper (manufactured by Seiko EpsonCorporation)

Paper 7: Photo•print paper 2

Paper 8: Super fine paper

<Evaluation 11: Fixing Property>

PM-770C was upgraded, using each ink set, gradation patterns of Y, M, C,R, G, B and Bk were printed, and the fixing property of the printedmatter obtained using each ink set was evaluated. The evaluation wasmade in accordance with the criteria shown below. Printing was carriedout using the evaluation papers shown below. The results are shown inTable 13.

“Evaluation Criteria”

A: Fixing properties of all the colors are good.

B: Fixing properties are somewhat insufficient in all the colors.

C: Fixing properties are insufficient in all the colors.

“Evaluation Papers”

Glazed paper 1: Photo•print paper 2

Glazed paper 2: PM Photographic paper

Glazed paper 3: Glazed film

<Evaluation 12: Uniformity of Gloss (Gloss Unevenness) of GradationPrints>

Using each ink set, gradation patters of Y, M, C, R, G, B and Bk wereprinted using PM-770C and the glossy feeling of the printed matterobtained by each ink set was visually observed. The evaluation was madein accordance with the criteria shown below. Printing was carried outusing the above-described evaluation papers (Glazed papers 1 to 3: soldby Epson). The results are shown in Table 13.

“Evaluation Criteria”

A: Gloss is uniform and gives no anxiety.

B: Gloss is somewhat ununiform.

C: Gloss is ununiform and gives anxiety as image.

TABLE 13 Color Developing Property Fixing Property Uneven GlossEvaluation Paper P.5 P.6 P.7 P.8 GP.1 GP.2 GP.3 GP.1 GP.2 GP.3 Example 4B B A A A A A A A A Example 5 B B A A A A A A A A Example 6 B B A A A AA A A A Compara- D D B C B C B C C B tive Example 2 P.5 to P.8: Paper 5to Paper 8 GP.1 to GP.3: Glazed paper 1 to Glazed paper 3

(Preparation of the Ink of Example 7 of the Invention)

The ink having the composition shown in Table 14 was prepared by thefollowing procedure as in the cases of preparing the inks ofabove-described Examples 1 to 3.

An aqueous medium not including the colorant obtained as described abovewas previously prepared, and the aqueous medium was gradually addeddropwise to the dispersion of the colorant described above in a stirredstate, followed by sufficient stirring. The mixture was filtered by amembrane filter of 5 μm to obtain the ink.

The surface tension of each ink was measured by an automatictensiometer, Type CBVP-Z, manufactured by Kyowa Kaimen Kagaku K. K. Theresults are shown in Table 14.

In Table 14 below, Olfin E1010 (manufactured by Nisshin Kagaku Kogyo K.K.), Olfin STG (manufactured by Nisshin Kagaku Kogyo K. K.), andSurfynol 465 (manufactured by Air Products and Chemicals Inc.) areacetylene glycol-based surface active agents, and Surfynol 61(manufactured by Air Products and Chemicals Inc.) is an acetylenealcohol-based surface active agent. Also, DEGmBE is diethylene glycolmonobutyl ether and TEGmBE is triethylene glycol monobutyl ether. Inaddition, in the table, Bk represents black, Y: yellow, M: magenta, LM:light magenta. C: cyan, and LC: light cyan.

(Ink Set of Example 7)

The ink set of Example 7 comprises a combination of “Bk, Y, M, LM, C andLC” as shown in Table 14 below.

TABLE 14 Example 7 Bk Y M LM C LC Colorant Colorant 4-A  7.5 — — — — —Colorant 4-B —  5.0 — — — — Colorant 4-C — — 5.5 1.5 — — Colorant 4-D —— — {circumflex over ( )}  4.5  1.0 Alkylene Olfin E1010  1.00 — — — — —glycol- Olfin STG — —  1.00  1.00 — — based Surfynol 465 — — — —  1.20 1.20 surfactant Acetylene Surfynol 61 —  0.50 — — — — alcoholsurfactant Glycol DEGmBE  5.00 — — — — — Ethers TEGmBE —  5.00 — — 10.0010.00 1,2- 1,2-Pentanediol —  2.00 — — — — Alkylene 1,2-Hexanediol — 3.00  5.00  5.00  3.00  3.00 glycol 1,6-Hexanediol — —  5.00  5.00 — —Glycerol Glycerol 14.00 14.00  9.00  9.00  9.00  9.00 Diethylene glycol— —  7.00  7.00  5.00  5.00 Thioglycol — —  3.50  3.50 — —1,3-dimethyl-2- —  2.00 — — — — imidazolidinone pH Triethanolamine  0.80 0.70  1.00  1.00  0.90  0.90 Controller Potassium — —  0.10  0.10 — —hydroxide Antifungal Proxel XL-2  0.03  0.03  0.03  0.03  0.03  0.03Agent Rust Benzotriazole  0.02  0.02  0.02  0.02  0.02  0.02 inhibitorWater Ion exchanged bal. bal. bal. bal. bal. bal. water Surface tension(mN/m) 34 34 34 34 32 32

(Evaluation of Ink)

<Evaluation 13: Printing Quality>

With respect to each ink (the inks of Example 7) of above-shown Table 7,using the ink let printer, MJ-930C (manufactured by Seiko EpsonCorporation), each 24 letters of upper case letters and lower caseletters of the alphabet were printed on each of the papers shown below.The letters printed were visually observed, and evaluated in accordancewith the following criteria.

SA: No blurring generates in the whole paper and the printing density ishigh.

AA: Blurring is not generated but the printing density is low ascompared with the SA lank.

A: Generation of blurring is slightly only observed on 2 or 3 papers.

B: Generation of blurring is slightly observed in all the papers.

C: Generation of blurring is many in all the papers.

The papers used for the evaluation are 12 kinds of papers including aConqueror paper, a Favorit paper, a Modo paper, a Rapid Copy paper, anEpson EPP paper, a Xerox P paper, a Xerox 4024 paper. a Xerox 10 paper,a Neenha Bond paper, a Ricopy 6200 paper, a golden-banded lily paper(recycled paper), and a Xerox R paper (recycled paper).

<Evaluation 14: Water Resistance>

To the printed portion of each of the printed matters obtained in theprinting quality test of Evaluation 13 was added dropwise 1 ml of ionexchanged water. The state thereof after 20 minutes was visuallyobserved, and the water resistance was evaluated in accordance with thefollowing criteria.

A: No change in all the papers.

B: The coloring material slightly flows out from the printed portion butthe letter can be recognized.

C: The coloring material flows out from the printed portion and sincethe outline of the printed letter is obscure, the recognition of theletter is difficult.

<Evaluation 15: Dispersion Stability (1)>

Each ink was placed in a glass-made sample bottle (50 ml) followed bytightly sealing, and the bottle was allowed to stand for 2 weeks at 60°C. Before and after allowing stand the bottle, the viscosity of the inkwas measured. The measurement was carried out using RheometrixScientific RFS2 under the conditions of 20° C. and 150 S⁻¹. The resultobtained was evaluated by the following criteria.

SA: The variation is less than ±0.02 mPa·s

AA: The variation is at leas ±0.02 and less than ±0.05 Pa·s

A: The variation is at least ±0.05 and less than ±0.1 Pa·s

B: The variation is at least ±0.1 and less than ±0.3 Pa·s

C: The variation is at least ±0.3 mPa·s

<Evaluation 16: Dispersion Stability (2)>

Each ink was placed in a glass-made sample bottle (50 ml) followed bytightly sealing, the bottle was allowed to stand for 2 weeks at 60° C.Existence of the generations of precipitates and foreign matters weredetermined, and the dispersion stability was evaluated in accordancewith the following criteria.

A: No generations of precipitates and foreign matters.

B: Precipitates or foreign matters are generated.

<Evaluation 17: Reliability of Clogging>

Each ink was packed in each head of an ink jet printer, MJ-930C,manufactured by Seiko Epson Corporation and letters were continuouslyprinted for 10 minutes. Thereafter, the printer was stopped and wasallowed to stand for 2 weeks under the environment of 40° C. and ahumidity of 25% without applying caps. After allowing to sand, letterswere printed again, the number (the number of returning actions)required for obtaining the same printing quality as that before allowingto stand was determined, and the evaluation was carried out by thefollowing criteria.

SA: By the returning action of from 0 to 1, the same printing quality asthat before allowing stand was obtained.

AA: By the returning actions of from 2 to 3, the same printing qualityas that before allowing stand was obtained.

A: By the returning actions of from 3 to 4, the same printing quality asthat before allowing stand was obtained.

B: By the returning actions of from 5 to 6, the same printing quality asthat before allowing stand was obtained.

C: Even by the returning actions of 7 times, the same printing qualityas that before allowing stand was not obtained.

<Evaluation 18: Ejection Stability>

With respect to each ink, using an ink jet printer, MJ-930C(manufactured by Seiko Epson Corporation), letters were continuouslyprinted on Xerox P papers. The states of the prints such as dotdeletion, the displacement of the ink-landing positions, etc., werevisually observed, and the ejection stability was evaluated inaccordance with the following criteria.

SA: Even by printing on at least 50,000 papers, dot deletion anddisplacement of the ink-landing positions do not occur.

AA: Within the number of printed papers of at least 10,000 and less than50,000, dot deletion and displacement of the ink-landing positionsoccur.

A: Within the number of printed papers of at least 1000 and less than10,000, dot deletion and displacement of the ink-landing positionsoccur.

B: Within the number of printed papers of at least 100 and less than1000, the dot deletion and displacement of the ink-landing positionsoccur.

C: Within the number of printed papers of less than 100, dot deletionand displacement of the ink-landing positions occur.

<Evaluation 19: Scrubbing Resistance>

Using the ink jet printer, MJ-930C (manufactured by Seiko EpsonCorporation), each ink was solid-color printed at 100% duty on the SuperFine exclusive glazed film (manufactured by Seiko Epson Corporation) ina region of 10 mm×10 mm. After allowing to stand for one hour at atemperature of 25° C., the above-described printed region was scrubbedusing a yellow aqueous fluorescent pen, ZEBRA PEN 2 (registered trademark) manufactured ZEBRA K. K., at a load of 500 g and at a speed of 10mm/second. Existence of the generation of soils was observed. Theresults were evaluated in accordance with the following criteria.

A: No stain generates by scrubbing two times.

B: Stain is not generated by one scrubbing but stain generates by thesecond scrubbing.

C: Stain generates by one scrubbing.

<Evaluation 20: Quick Drying Property>

With respect to each ink, using the ink jet printer, MJ-930C(manufactured by Seiko Epson Corporation), a solid-color was printed at100% duty on the Xerox P paper in a region of 10 mm×10 mm. After 10seconds, a new Xerox P paper was placed on the printed portion, and aweight of 300 g was placed thereon, following by standing for 10seconds. The weight was then removed, and the ink adhesion state on thenew P paper was confirmed. The results were evaluated in accordance withthe following criteria.

A: No ink adhesion.

B: Ink adhesion is observed.

The results of above-described evaluations 13 to 20 are shown in Table15 below.

TABLE 15 Example 7 Bk Y M LM C LC Evaluation 13: Printing SA SA SA — SA— quality Evaluation 14: Water A A A A A A resistance Evaluation 15:Dispersion SA SA SA SA SA SA stability (1) Evaluation 16: Dispersion A AA A A A stability (2) Evaluation 17: Clogging AA AA AA AA AA AAreliability Evaluation 18: Ejection SA SA SA SA SA SA stabilityEvaluation 19: Scrubbing A A A A A A resistance Evaluation 20: Quickdrying A A A A A A property

<Evaluation 21: Color Developing Property> <Evaluation 22: FixingProperty> <Evaluation 23: Uniformity of Gloss (Gloss Unevenness) ofGradation Print>

With respect to the ink of Example 7, the evaluations of the “Evaluation21: Color developing property”, “Evaluation 22: Fixing property” and“Evaluation 23: Uniformity of gloss (gloss unevenness) of gradationprint” were carried out under the same conditions of “Evaluations 10 to12” described above. The results are shown in Table 16.

TABLE 16 Color Developing Property Fixing Property Uneven GlossEvaluation Paper P.5 P.6 P.7 P.8 GP.1 GP.2 GP.3 GP.1 GP.2 GP.3 Example 7B B A A A A A A A A P.5 to P.8: Paper 5 to Paper 8 GP.1 to GP.3: Glazedpaper 1 to Glazed paper 3

As is clear from each table described above, it can be seen thataccording to Examples 1 to 7 of the invention, printed images of highquality are obtained on evaluation papers and images of high qualityhaving a high printing density and being excellent in the colordeveloping property can be obtained. Also, it can be seen that Examples4 to 6 are excellent in, for example, the color developing property ascompared to Example 7.

<Industrial Applicability>

By the ink jet recording ink set of the invention, printed images ofhigh quality are obtained with respect to recording media of ink jetrecording exclusive papers such as plain papers, coated papers, etc.,images of high quality having a high printing density and beingexcellent in the color developing property can be obtained, and the inkjet recording ink set of the invention gives excellent working effectsin dispersion stability, ejection stability, and storage stability.

What is claimed is:
 1. An ink jet recording ink set comprising aplurality of inks, each ink comprising at least a colorant encapsulatinga pigment with a polymer, a penetrating agent comprising a surfaceactive agent selected from the group consisting of an acetyleneglycol-based surface active agent and an acetylene alcohol-based surfaceactive agent, and water, wherein said ink set comprises a combination ofblack, yellow, magenta, and cyan inks, and wherein the polymer in eachof the black, yellow, magenta and cyan inks is a polymer of apolymerizable surface active agent and a monomer.
 2. The ink jetrecording ink set according to claim 1, wherein the black, yellow,magenta, and cyan inks comprise a combination of at least one kind of ablack ink, at least one kind of yellow ink, at least one kind of magentaink, and at least one kind of a cyan ink, respectively.
 3. The ink jetrecording ink set according to claim 1 wherein the black, yellow,magenta, and cyan inks comprise a combination of at least one kind of ablack ink having a first pigment concentration, at least one kind of ayellow ink having a second pigment concentration, at least one kind of amagenta ink having a third pigment concentration, and at least one kindof a cyan ink having a fourth pigment concentration, each of said first,second, third and fourth pigment concentrations being different.
 4. Theink jet recording ink set according to claim 1, wherein the black inkcomprises C.I. Pigment Black 7; the yellow ink comprises one kind or twoor more kinds of pigments selected from the group consisting of C.I.Pigment Yellow 55, 74, 110, 128, 150, 155 and 180; the magenta inkcomprises one kind or two or more kinds of pigments selected from thegroup consisting of C.I. Pigment Red 122, 202, and 209: and the cyan inkcomprises one kind or two or more kinds of pigments selected from thegroup consisting of C.I. Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6and
 16. 5. The ink jet recording ink set according to claim 1, whereinthe colorant in each ink is present in an amount from 0.5 to 30% byweight.
 6. The ink jet recording ink set according to claim 1, whereinthe polymer in each ink comprises, as a main component, a polymerselected from the group consisting of a polyacrylic acid ester, astyrene-acrylic acid ester copolymer, a polystyrene, a polyester, apolyamide, a polyimide, a silicon-containing polymer, and asulfur-containing polymer.
 7. The ink jet recording ink set according toclaim 6, wherein the polymer is a polymer having a crosslinkedstructure.
 8. The ink jet recording ink set according to claim 7,wherein the polymer having a crosslinked structure is a polymer of adispersing agent having a polymerizable group and a crosslinkablemonomer.
 9. The ink jet recording ink set according to claim 7, whereinthe colorant is obtained by dispersing the pigment or the dye or both inwater with a dispersing agent having a polymerizable group, and thenadding at least a crosslinkable monomer and a polymerization initiatorto cause polymerization.
 10. The ink jet recording ink set according toclaim 1, wherein the polymerizable surface active agent has apolymerizable group, a hydrophobic group, and a hydrophilic group in itsstructure.
 11. The ink jet recording ink set according to claim 10,wherein the polymerizable group is selected from the group consisting ofa vinyl group, an acrylic group, an acryloyl group, and a methacryloylgroup.
 12. The ink jet recording ink set according to claim 10, whereinthe hydrophilic group is selected from the group consisting of acarbonyl group, a carboxyl group, a hydroxyl group, a sulfonic acidgroup, and salts thereof.
 13. The ink jet recording ink set according toclaim 1, wherein each ink of the ink jet recording ink set furthercontains glycerol and the surface active agent is present in each ink inan amount sufficient to make the surface tension of each ink 40 mN/m orlower.
 14. The ink jet recording ink set according to claim 1, whereinthe penetrating agent further comprises at least one member selectedfrom a glycol ether and a 1,2-alkylene glycol.
 15. The ink jet recordingink set according to claim 14, wherein the penetrating agent comprises(a) 2,4-dimethyl-5-hexyne-3-ol,2,4,7,9-tetramethyl-5-decyne-4,7-diol,3,6-dimethyl-4-octyne-3,6-diol or (b) 2,4-dimethyl-5-hexyne-3ol,2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol,having added with at most 30, on average, ethyleneoxy groups orpropyleneoxy groups or (c) both.
 16. The ink jet recording ink setaccording to claim 14, wherein the glycol ether is one member or amixture or two or more members selected from the group consisting ofdiethylene glycol mono alkyl ether wherein the alkyl has 4 to 8 carbonatoms, triethylene glycol mono alkyl ether wherein the alkyl has 3 to 6carbon atoms, and dipropylene glycol mono alkyl ether wherein the alkylhas 3 to 6 carbon atoms.
 17. The ink jet recording ink set according toclaim 16, comprising the 1,2-alkylene glycol, wherein the 1,2-alkyleneglycol is a 1,2-alkyl diol with the alkyl having from 4 to 10 carbonatoms.
 18. The ink jet recording ink set according to claim 16,comprising propylene glycol monobutyl ether or dipropylene glycolmonobutyl ether or both.
 19. The ink jet recording ink set according toclaim 14, wherein the 1,2-alkylene glycol is 1,2-pentanediol or1,2-hexanediol or both.
 20. The ink jet recording ink set according toclaim 1, wherein the penetrating agent further comprises 1,2-alkyleneglycol.
 21. The ink jet recording ink set according to claim 1, whereinthe pigment for the colorant of each ink is encapsulated with thepolymer by a process comprising the steps of (a) mixing an organicsolvent phase comprising a polymerizable group, a hydrophobic group, acrosslinking agent, an organic solvent and a neutralizing agent withwater in the presence of the pigment to form an emulsion, and (b)initiating a crosslinking reaction to form the polymer encapsulating thepigment and distilling off the organic solvent.
 22. An ink jet recordingink set comprising a plurality of inks, each ink comprising at least acolorant encapsulating a pigment with a polymer, a penetrating agentcomprising a surface active agent selected from the group consisting ofan acetylene glycol-based surface active agent and an acetylenealcohol-based surface active agent, and water, wherein said ink setcomprises a combination of black, yellow, magenta, cyan, orange andgreen inks, and wherein the polymer in each of the black, yellow,magenta, cyan, orange and green inks is a polymer of a polymerizablesurface active agent and a monomer.
 23. The ink jet recording ink setaccording to claim 22, wherein the black ink comprises C.I. PigmentBlack 7; the yellow ink comprises one kind or two or more kinds ofpigments selected from the group consisting of C.I. Pigment Yellow 55,74, 110, 128, 150, 155 and 180; the magenta ink comprises one kind ortwo or more kinds of pigments selected from the group consisting of C.I.Pigment Red 122, 202 and 209: the cyan ink comprises one kind or two ormore kinds of pigments selected from the group consisting of C.I.Pigment Blue 15, 15:1, 15:2, 15:3, 15:4, 15:6 and 16; the orange inkcomprises one kind or two or more kinds of pigments selected from thegroup consisting of C.I. Pigment Orange 36 and 43; and the green inkcomprises one kind or two or more kinds of pigments selected from thegroup consisting of C.I. Pigment Green 7 and
 36. 24. The ink jetrecording ink set according to claim 22, wherein the penetrating agentfurther comprises at least one member selected from a glycol ether and a1,2-alkylene glycol.
 25. The ink jet recording ink set according toclaim 22, wherein the colorant in each ink is present in an amount from0.5 to 30% by weight.
 26. The ink jet recording ink set according toclaim 22, wherein the polymer in each ink comprises, as a maincomponent, a polymer selected from the group consisting of a polyacrylicacid ester, a styrene-acrylic acid ester copolymer, a polystyrene, apolyester, a polyamide, a silicon-containing polymer, and asulfur-containing polymer.
 27. The ink jet recording ink set accordingto claim 22, wherein the polymer in each ink is a polymer of apolymerizable surface active agent and a monomer.
 28. The ink jetrecording ink set according to claim 22, wherein each ink of the ink jetrecording ink set further contains glycerol and the surface active agentis present in each ink in an amount sufficient to make the surfacetension of each ink 40 m/N/m or lower.
 29. The ink jet recording ink setaccording to claim 22, wherein the penetrating agent further comprises1,2-alkylene glycol.